Find the Decrease in Value , Original and New Value and Percentage Decrease | Grade 7 | MC |
Summary
TLDRTeacher 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
- ๐ The class is focused on calculating the decrease in value and the percentage of decrease.
- ๐ข The formula for calculating the percentage of decrease is: (Amount of Decrease / Original Value) * 100.
- ๐ To find the amount of decrease, subtract the new value from the original value.
- ๐ Example 1 demonstrates calculating the decrease and percentage of decrease when both original and new values are given.
- ๐งฎ The script provides a step-by-step manual calculation for the percentage of decrease without a calculator.
- ๐ Example 2 shows how to find the new value when the percentage of decrease and original value are known.
- ๐ The process involves substituting values into the percentage decrease formula and solving for the unknown.
- ๐ The script emphasizes the importance of balancing equations when transposing terms.
- ๐ค Example 3 is a practice problem for students to apply the learned concepts.
- ๐ 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.
- ๐จโ๐ซ 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
๐ 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.
๐ข 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%.
๐ 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.
๐ 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.
Mindmap
Keywords
๐กDecrease
๐กPercentage of Decrease
๐กOriginal Value
๐กNew Value
๐กAmount of Decrease
๐กFormula
๐กDivide
๐กMultiply
๐กCalculator
๐กCross Multiplication
๐กTransposing
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
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