Understanding Percentage Changes

In this video, Lucy explains how to calculate percentage changes, a skill useful in various real-life scenarios such as stock value changes, rainfall comparison, and unemployment figures. The video covers the concept of multipliers, which are used to determine percentage increases or decreases. Lucy provides examples, including calculating the percentage decrease in HIV-related deaths and the sale price of a car. The video concludes with practice questions and emphasizes the importance of understanding whether a question is about percentage change or finding a percentage of a value.

What is one real-life application of calculating percentage changes?

• Determining the height of a building

• Calculating the area of a circle

• Comparing stock values

• Measuring the speed of a car

What is the formula used to calculate percentage changes?

• New value = Old value + Multiplier

• New value = Old value / Multiplier

• New value = Old value * Multiplier

• New value = Old value - Multiplier

In the context of percentage changes, what does a multiplier less than 1 indicate?

• No change

• An error in calculation

• A percentage decrease

• A percentage increase

If a value decreases from 100 to 80, what is the multiplier?

• 1.2

• 0.8

• 1.8

• 0.2

What is the percentage decrease if the multiplier is 0.367?

• 36.7%

• 63.3%

• 26.7%

• 73.3%

In the second example, what is the original price of the car?

• $5,500

• $5,200

• $6,500

• $7,200

What is another term for finding the original value in percentage change problems?

• Direct percentages

• Indirect percentages

• Reverse percentages

• Forward percentages

What should you do if one value isn't clearly older or newer than the other?

• Assume the first value is older

• Assume the second value is older

• Ignore the question

• Treat it as a finding a percentage question

What is a common mistake people make with percentage change questions?

• Forgetting to multiply

• Adding instead of subtracting

• Confusing percentage change with percentage of

• Using the wrong units

What is the key formula to remember for percentage changes?

• New = Old * Multiplier

• New = Old / Multiplier

• New = Old - Multiplier

• New = Old + Multiplier