Understanding Percentage Increase & Decrease

Understanding percentage increase and decrease helps you figure out how things grow or shrink over time. Imagine a price going up or a discount being applied to a sale—these are great examples of percentage increase and decrease in action.

 

What is Percentage Increase and Decrease?

• Percentage Increase: When a value goes up, like prices or savings, we calculate how much it has increased as a percentage of the original amount.
• Percentage Decrease: When a value goes down, like a discount or reduction, we calculate how much it has decreased as a percentage of the original amount.

General Formula

To calculate the percentage increase or decrease: $$\text{Percentage Change} = \frac{\text{Change in Value}}{\text{Original Value}} \times 100$$

 

How to Calculate Percentage Increase

To calculate a percentage increase:

1. Find the difference (new value - original value).
2. Divide the difference by the original value.
3. Multiply by 100 to get the percentage increase.

Formula

If the new value is greater than the original: $$\text{Percentage Increase} = \frac{\text{New Value} - \text{Original Value}}{\text{Original Value}} \times 100$$

Example: Price Increase

The price of a book increased from $\pounds 50$ to $\pounds60$. Find the percentage increase.

1. Find the difference: $$\text{Difference} = 60 - 50 = 10$$
2. Divide by the original value (50) and multiply by 100: $$\text{Percentage Increase} = \frac{10}{50} \times 100 = 20\%$$

So, the price increased by $20\%$

 

 

 

 

 

 

 

How to Calculate Percentage Decrease

To calculate a percentage decrease:

1. Find the difference (original value - new value).
2. Divide the difference by the original value.
3. Multiply by 100 to get the percentage decrease.

Formula

If the new value is less than the original: $$\text{Percentage Decrease} = \frac{\text{Original Value} - \text{New Value}}{\text{Original Value}} \times 100$$

Example: Price Decrease

The price of a phone dropped from $\pounds200$ to $\pounds150$. Find the percentage decrease.

1. Find the difference: $$\text{Difference} = 200 - 150 = 50$$
2. Divide by the original value (200) and multiply by 100: $$\text{Percentage Decrease} = \frac{50}{200} \times 100 = 25\%$$

So, the price decreased by $25\%$.