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%.