Find the Decrease in Value , Original and New Value and Percentage Decrease | Grade 7 | MC |

Summary

Teacher MJ's video tutorial focuses on calculating the decrease in value and the percentage of decrease. Using clear examples, the instructor demonstrates how to find the amount of decrease by subtracting the new value from the original value. The percentage decrease is then calculated by dividing the decrease by the original value and multiplying by 100. The video covers various scenarios, including when only the original value and decrease are known, and when only the new value and decrease are provided. It also includes a step-by-step manual calculation of percentages without a calculator and encourages viewers to practice with example number three.

Takeaways

• 📚 The class is focused on calculating the decrease in value and the percentage of decrease.
• 🔢 The formula for calculating the percentage of decrease is: (Amount of Decrease / Original Value) * 100.
• 📉 To find the amount of decrease, subtract the new value from the original value.
• 📈 Example 1 demonstrates calculating the decrease and percentage of decrease when both original and new values are given.
• 🧮 The script provides a step-by-step manual calculation for the percentage of decrease without a calculator.
• 📝 Example 2 shows how to find the new value when the percentage of decrease and original value are known.
• 🔄 The process involves substituting values into the percentage decrease formula and solving for the unknown.
• 📑 The script emphasizes the importance of balancing equations when transposing terms.
• 🤔 Example 3 is a practice problem for students to apply the learned concepts.
• 📊 Examples 4 and 5 illustrate scenarios where the new value and the amount of decrease are given, and the original value and percentage decrease are calculated.
• 👨‍🏫 Teacher MJ encourages students to practice and ask questions to ensure understanding of the material.

Q & A

What is the formula to calculate the percentage of decrease?

The formula to calculate the percentage of decrease is: Percentage of Decrease = (Amount of Decrease / Original Value) x 100.

How do you find the amount of decrease between two values?

The amount of decrease is found by subtracting the new value from the original value: Amount of Decrease = Original Value - New Value.

In the example where the original value is 120 and the new value is 90, what is the decrease and the percentage of decrease?

The decrease is 30 (120 - 90), and the percentage of decrease is 25% (30 / 120 x 100).

How do you calculate the percentage of decrease without a calculator?

To calculate the percentage of decrease without a calculator, you divide the amount of decrease by the original value and then multiply by 100. For example, if the decrease is 30 and the original value is 120, you would divide 30 by 120 to get 0.25, then multiply by 100 to get 25%.

What is the purpose of moving the decimal point when multiplying by 100 in the percentage calculation?

Moving the decimal point two places to the right when multiplying by 100 converts a decimal to a percentage. For example, 0.25 multiplied by 100 becomes 25%.

In the case where you have the percentage of decrease and the original value but not the new value, how do you find the new value?

If you have the percentage of decrease and the original value, you can find the new value by first calculating the amount of decrease using the formula (Percentage of Decrease / 100) x Original Value, and then subtracting this amount from the original value.

What is the significance of the 'nv' notation used in the script?

The 'nv' notation stands for 'new value' and is used when the new value is not given and needs to be calculated based on the percentage of decrease and the original value.

How do you verify that the calculated new value and the given percentage of decrease align correctly?

To verify, calculate the amount of decrease using the new value and original value, and then apply the percentage of decrease formula to see if it matches the given percentage. If the calculated percentage matches the given percentage, the new value is correct.

What is the method to find the original value when you have the new value and the amount of decrease?

To find the original value when you have the new value and the amount of decrease, simply add the amount of decrease to the new value: Original Value = New Value + Amount of Decrease.

Can you provide an example of how to calculate the percentage of decrease when the original value is 1800 and the amount of decrease is 540?

To calculate the percentage of decrease when the original value is 1800 and the amount of decrease is 540, use the formula: (540 / 1800) x 100 = 30%.

Outlines

00:00

📘 Introduction to Calculating Decrease and Percentage Decrease

Teacher MJ introduces the topic of calculating the decrease in value and the percentage of decrease in a class setting. The formula for calculating percentage decrease is explained as the amount of decrease divided by the original value, multiplied by 100. An example is provided where the original value is 120 and the new value is 90, resulting in a decrease of 30. The percentage decrease is then calculated by dividing the decrease (30) by the original value (120) and multiplying by 100, resulting in a 25% decrease. The process is demonstrated both manually and using a calculator for clarity.

05:01

🔢 Advanced Calculations Without the New Value

The script continues with a more complex example where the new value is not given, and the percentage of decrease is known (38%). The original value is provided as 145. The teacher guides through the process of substituting the known values into the formula and solving for the new value (nv). The calculation involves cross-multiplication and results in a new value of 89.9. The amount of decrease is then calculated by subtracting the new value from the original value, yielding a decrease of 55.1. The calculation is verified by checking if the percentage of decrease matches the given 38%.

10:02

📊 Summing Up to Find Original Value and Calculate Percentage Decrease

In this section, the script explains how to find the original value when given the new value and the amount of decrease. The process involves adding the new value to the decrease to get the original value. The example provided uses values of 1260 (new value) and 540 (decrease), summing up to an original value of 1800. The percentage of decrease is then calculated using the formula, resulting in a 30% decrease. The teacher emphasizes the importance of using a calculator for large numbers and provides a step-by-step guide on how to perform the calculations.

15:07

🎓 Final Example and Conclusion

The final example provided involves adding two values to find the original value (1500 + 4500 = 6000) and then calculating the percentage of decrease using the formula. The amount of decrease is 4500, and when divided by the original value (6000) and multiplied by 100, it results in a 75% decrease. The teacher concludes the lesson by encouraging students to answer a third example on their own and to ask questions if needed. The video ends with a reminder to like, share, and subscribe for more educational content, and a farewell from Teacher MJ.

Keywords

💡Decrease

Decrease refers to a reduction in size, number, or amount. In the context of the video, it is used to describe the reduction from an original value to a new value. The script explains how to calculate the decrease by subtracting the new value from the original value, as seen in the example where the original value is 120 and the new value is 90, resulting in a decrease of 30.

💡Percentage of Decrease

The percentage of decrease is a measure of how much one quantity has decreased relative to another, expressed as a percentage. The video script introduces a formula to calculate this: (amount of decrease / original value) * 100. It is used to quantify the decrease, such as calculating a 25% decrease when the decrease is 30 and the original value is 120.

💡Original Value

Original value is the starting amount or value before any changes occur. The video script uses the original value as a reference point to calculate the decrease and the percentage of decrease. For instance, in the script, an original value of 120 is given, and from this, decreases are calculated to find the new values and percentages of decrease.

💡New Value

New value represents the amount or value after a decrease has occurred. The video script discusses how to find the new value by subtracting the decrease from the original value. It is also used in the formula for calculating the percentage of decrease, as the value to which the original value is compared.

💡Amount of Decrease

Amount of decrease is the numerical difference between the original value and the new value. The video script provides a clear example of calculating the amount of decrease by subtracting the new value (90) from the original value (120), resulting in an amount of decrease of 30.

💡Formula

A formula in this context is a mathematical equation used to calculate a specific value or result. The video script presents a formula for calculating the percentage of decrease, which is crucial for understanding the quantitative aspect of changes in values. The formula is integral to the video's educational content, guiding viewers on how to perform the calculations.

💡Divide

Divide is a mathematical operation that involves splitting a number into a certain number of equal parts. In the video script, division is used in the formula to calculate the percentage of decrease by dividing the amount of decrease by the original value, as shown when dividing 30 by 120 to find the percentage decrease.

💡Multiply

Multiply is a mathematical operation that combines a number by another a certain number of times. The video script instructs viewers to multiply the result of the division by 100 to convert it into a percentage, such as multiplying 0.25 by 100 to get 25%.

💡Calculator

A calculator is a device or software used to perform mathematical calculations. The video script mentions the use of a calculator as a tool to simplify the process of dividing large numbers, which is helpful when calculating percentages of decrease without manual calculation.

💡Cross Multiplication

Cross multiplication is a technique used to solve equations, particularly those involving fractions. The video script refers to cross multiplication when solving for the new value in an equation where the percentage of decrease and the original value are known, illustrating a method to isolate and solve for the unknown variable.

💡Transposing

Transposing in algebra involves changing the position of a term from one side of an equation to the other, often changing its sign in the process. The video script uses transposing to solve for the new value, explaining how to move terms across the equals sign while adjusting their signs accordingly.

Highlights

Introduction to the topic of calculating the decrease in value and percentage of decrease.

Explanation of the formula for calculating the percentage of decrease.

Example 1: Calculation of decrease and percentage of decrease given original and new values.

Step-by-step manual calculation of the decrease without a calculator.

Verification of the manual calculation using a calculator for accuracy.

Example 2: Solving for new value when given percentage of decrease and original value.

Cross-multiplication technique to find the new value in Example 2.

Double-checking the calculated percentage of decrease in Example 2.

Example 3: Challenge for students to apply the learned method.

Example 4: Calculation of original value and percentage of decrease given new value and decrease.

Example 5: Calculation of original value and percentage of decrease using the same method as Example 4.

Emphasis on the importance of adding the new value and decrease to find the original value.

Encouragement for students to practice and apply the formulas learned.

Invitation for students to ask questions and engage in the learning process.

Conclusion and farewell from Teacher MJ, encouraging students to have a great day.

Transcripts

Hi guys good day It's me teacher MJ our

topic for today Class is we're going to

find the decrease the original value the

new value and the percentage of decrease

so without further Ado let's do this

topic now this will we the formula class

in getting the percentage of decrease we

have the percentage of decrease or the

percent decrease So I will just write

the percent symbol class since we don't

have enough space equals the amount of

decrease divided by original value times

100 so let's start with example number

one class you have given original value

and you have given new value and you're

told to find the decrease or the amount

of decrease and the percentage of

decrease So if you have given original

value and the new value class It's easy

for us to find the decrease and the

percentage of decrease so to find the

decrease or the amount of

decrease amount of decrease that would

be the original value minus the new

value All right so to find the decrease

or the amount of decrease original value

minus the new value original value

that's

120 minus the new value that's 90 120

Min 90 that would be

30 All right that's it that's the answer

for this one for the decrease that would

be

30 and to find the percentage of

decrease we can just simply use this

formula All right so percentage of

decrease equals the amount of decrease

that would be 30 once second class the

amount of decrease original value minus

new value TH that would be 30 so

therefore amount of decrease that is

30 divide original value that's

120 30 / 120 Tim

100 All right now if the teacher will

not allow you to use calculator you need

to do it manually you need to divide 30

by 120 so divide 30 div

120 so 30 div by 120 of course that's

cannot be we need to borrow one zero you

put a point and then you borrow one zero

now once you put a point here you also

put a point on the top you align the

points class Okay and then you think

this one class as 300 it's not 30.0 you

think this one as 300 so once again 30 /

120 that's cannot be we need to add one

zero once you add one zero you put a

point you also put a point on the to you

align class so 300 div 120 of course the

2 and then 2 * 120 that would be

240 subtract 300 - 240 that would be

60 All right and then you need to add

another zero because you cannot divide

60 by 120 you need to add Again one zer

add one zero So this will be

600 and then 600 / 120 of course there

would be 5 right 6 600 di 120 that's 5

let's check let 120 * 5 5 * 0 is 0 5 * 2

is 10 0 Car 1 5 * 1 is 5 + 1 is 6

600 All right so 600 / 120 that is 5 5 *

120 that is 600 subtract that is z0 Okay

so 30 / 120 That's

0.25 all right So this is

0.25 Tim 100 now once you multiply a

decimal class by hundreds simply move

the decimal point class left to right

Twice one then two and this will be the

decimal point so therefore This is 25

and then you put percent since We're

Looking for the percentage of decrease

that's it CL All set for number one Easy

for number one CL since you have the new

value and the original values if you

want to use your

calculator Okay simply divide this 130

div 120

course that's 25 you multiply by 100

that would be 25 Okay multiply by 100

that would be 25

25% All right Let's have example number

two now for number two class quite

complicated since we don't have the new

value and the

decrease so to solve for number two

class we be substituting the value of

percentage of decrease we have

38% and for the original value We will

substitute that for the amount of

decrease let me just explain number two

class once again class you plug in this

value class for the percentage of

decrease that would be 38 once again the

percentage of decrease we have given for

number two that's

38 and then equals once again CL the

amount of decrease since we don't have

the new value we need to write original

value minus the new value once again let

me just explain this one class amount of

decrease Okay amount of

decrease that would be original value

minus then value right there m class for

the amount of decrease So we cannot get

the amount of decrease because we don't

have Okay we don't have the new value

because the amount of decrease it says

original value minus the new value but

we don't have the new value therefore we

need to write this one we need to write

this equation that would be original

value minus the new value

divide Okay once again this is just the

same CL amount of decrease is equ

original value minus the new value So

this is just the same CL amount of

decrease original value minus the new

value this is just the same All right so

do we have original value Yep we have

original value that's 145 so instead of

original value we can write

145 Okay we can write

145 because the amount of decrease

original value minus the new value we

have the original value that's

145 divide original value that's 140 5

and we don't have the new value times

100 All right so I hope you're not

confused class once again this 38 came

from the percentage of decrease that's

38% equals the amount of decrease that

would be original value minus the new

value Okay original value minus the new

value divided by original value that is

145 for the new value class We just

write nv because we don't have the value

of the new value You can put x there is

this the same class if I will put x Is

that okay sir if I will put x for the

new value Yep you can use any variable

you can use y you can use a you can use

B you can use n you can use X okay or

Let's just write nv new

value All right so to find the new value

class we need to multiply both sides by

1 over 100 so that we can eliminate this

one and then we can do cross

Multiplication Later on once again CL

multiply both sides by 1 over 100

multiply both sides by 1 over 100 now

you will be asking question Why is that

sir Why do we need to multiply both

sides sir by 1 over 100 so that we can

cancel this out once again so that we

can cancel this out because

100 MP by 1 /

100 you can just simply cancel this out

100 div 100 that is 1 right or if it's

hard for you to understand that always

remember this one us that a whole number

there is a Denominator of one right 100

there is a Denominator of one multiply

fractions multiply the numerators 100

Tim 1 that's

100 1 * 100 that would be 100 100 / 100

that is 1 so therefore we can just

simply cancel this outl 100 Tim 1 over

100 that would be 100 / 100 that is

equals to 1 All right so we can cancel

this

out and then we multiply this one once

again CL once you multiply 1 over 100 on

the right of the equal side you also do

that on the left side CL Okay once you

multiply a number on the right you also

do that on the left side to make the

equation balance CL All right so

multiply this one 1 / 100 1 / 100 Tim 38

once again understood that there's one

here so 1 * 38 that's 38 100 * 1 that's

100

So if you're dividing class by 100 once

again a whole number divided by 100 you

just move the decimal point right to

left Twice Okay move this one right to

left Twice 1 two and this will be

0.38 once again dividing this one by a

whole number by 100 simply move decimal

point right to left Twice right to left

Twice 1 two this will be 0.38 but if

you're confused let's use your

calculator Okay 38 8 / 100 you will get

0.38 Okay

0.38 all right so let me just erase this

one

0.38 So this is

0.38 equals copy this one We just cancel

100 copy this one

145 -

nv /

145 All right to get the value of NB we

can do cross Multiplication so

understood that there's one here cross

multiply

All right cross

multiply So this will be 0.38 Tim 145 so

0.38 Tim

145

equ 1 times this equation that would be

copy k 1 times this equation that is

copy copy is equation

145 Min

nv All right and then you multiply this

one CL

0.38 100

45

0.38 *

145 so that would be 55.1 I hope you see

this one 0.38 Tim

145 55.1 So this is

55.1 equ

145 -

nv All right so to get the value of nv

so to get the value of NB you can just

simply transpose this one nv from right

to left Okay transpose nv from right to

left and then transpose 55.1 from left

to right okay because we need to have we

need to get positive nv CL once again

transpose nv from right to

left All right and then we transpose 55

from left to

right All right So that's it let you

just simply transpose this one from

right to left This is negative It will

be positive one this is positive It will

be negative so I hope you understand

this one CL sir Why do we need to

transpose nv the new value from right to

left so that CL It will be positive Okay

It Will Be positive and the remaining

equation CL in this in the left side of

this equal side It will be nv so we need

to transpose this number from left to

right and you change the sign CL so let

me just erase this part CL I hope you

get this one CL once again CL if you

have some questions do not hesitate to

ask us put your question in the comment

section down below so once again we

transpose nv from right to left This is

negative It will be positive

nv All right equals copy 145 do not

change the sign class of

145 because 145 is still on the right

side of the equal sign We just simply

transpose 55.1 from left to right This

is positive It will be - 55.1

All right and then this will be

nv equ

145 - 55.1 and your all

set All right so

145 Min

55.1 and this will be

89.9 Okay once again

145 -

55.1 the answer is 89 9 that's it plus

all

set the new value is

89.9 So new value class that is

89.9 This is

89.9 that's it CL all

set All right so the amount of decrease

let simply subtract this one

145 minus once again original value

minus the new value

145 Min 8

89.9 the answer is

55.1 the amount of decrease that's

55.1 that's it CL all set Okay all set

CL for example number two All right and

then you can Double check your answer

with regards to this formula if we

really get

38% Okay let's Double check number two

let's check if we get 38% let's use our

calculator amount of decrease that's

55.1 again this is the amount of

decrease

55.1 divide original value original

value that's 145

145 equals Tim 100 Tim 100 you get 38%

all set CL that's the answer for number

three CL All right So you try this one

class number three and you put your

answer in the comment section down below

for number three CL same solution with

number two Okay so you try this one CL

put your answer the comment section down

below

let me check if you really understand

our topic all right Let's have example

number four so for number four class we

have given new value and the and the

amount of decrease once again CL Check

this one out CL for number one class

Okay Look at Take A Look with number one

class we have given

120 90 and we have given amount of

decrease to get the original value class

if you have given decrease and the new

value we can just simp add is up right

90 + 30 that's 120 therefore to get the

original value we can just simply add is

up once again let's Take a Look at

number one we have original value we

have new value and the decrease to get

the decrease We just simply subtract

original value by the new value right

120 Min 90 that's 30 and to get original

value we can just simply add this up

right 90 + 30 that would be 120

therefore to get the original value we

can just simply add this up

1260 plus 540 that would be 1,800 so

This is

1,800 so 1,800 now can we find the

percentage of decrease Yup we can

Actually find the percentage of decrease

because we have the amount of decrease

we have the original value and the new

value so find the percentage of

decrease So this will be the amount of

decrease that's 540

divide original value that's

1,800 Tim

100 easy right for number four so once

again if you have given new value and

the decrease we can just simply add this

up once you add this up that would be

your original value and use the formula

class in getting the percentage of

decrease so amount of decrease the

decrease that's

540 divide original value that's 1,800

Tim 100 so simply use your calculator

class I hope that your teacher class

will allow you to use calculator

especially class if you have large

numbers so

540 div

1,800 So this will be 0.3 so

0.3 Tim 100 once again just simply move

decimal point left to right Twice 1 Then

two Okay you add one zer So this will be

equal to 30 and would be 30% you add

percent less so once again

0.3 Tim 100 that would be 30 so 30% will

set

C that's it c for example number

4 All right so once again Let's have

example number five last

one so once again to get the original

value we can just simply add up

1,500 Plus 4,500

and the answer is 6,000 so This is

6,000 and to get the percentage of

decrease we can just simply apply this

formula so amount of decrease we have

4,500 divide original value that's

6,000 4,500 div by original value Tim

100 and then simply use your calculator

4,500 div 6,000 sun so that will be

0.75 Tim 100 simply move the decimal

point last left to right Twice 1 Then 2

and that would be

75 then you put percent that's it that's

all

set

75% easy right for numbers 4 and 5 So

that's it CL All set so once again CL Do

not forget CL to answer number three for

me to check if you really understand

this topic if you have some questions do

not hesitate to ask so once again I hope

you learn something new today If you

like this video Do not forget to like

share and subscribe you share to your

friends and your classmates so that we

can help more students once again this

is teacher MJ Have a great day CL

Goodbye for now Byebye