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# 7th Grade - Application of Percentage

## Introduction

• Percentages have many real-life applications.
• Discounts and percent increases in price are usually expressed in percentages.
• From your laptop or phone's battery and school test scores to your home or personal loan interest, the use of percent is widespread.

## What Percent One Number is of Another

• To find what percent one number is of another, divide the number before "is" by the number after "of".

## Finding the Base

• To solve a question like 30 is 60% of what number? First, divide the number by the percent number and then convert the percent number to decimal.

## Percent Increase and Decrease

• To find the % increase or decrease, divide the change by the initial/starting value.
• Percent increase or decrease =
• Change = old value - new value

## Examples

1) 30 is 60% of what number?

= $\frac{30}{60%}$

Remove the % sign and move the decimal two places to the left.

$=\frac{30}{0.60}$

$=\frac{300}{6}$

2) 25 is 40% of what number?

$=\frac{25}{40%}$

Remove the % sign and move the decimal two places to the left.

$=\frac{25}{0.4}$

$=\frac{250}{4}$

3) 40 is 120% of what number?

Remove the % sign and move the decimal two places to the left.

$=\frac{40}{1.2}$

$=\frac{400}{12}$

4) 30 is what percent of 50?

$\frac{30}{50}=\frac{3}{5}$

$\frac{3}{5}=0.6$

(Move the decimal point two places to the right to convert the decimal to a percent.)

5) 20 is what percent of 25?

$\frac{20}{25}=\frac{4}{5}$

$\frac{4}{5}=0.8$

0.8 = 80%  (Move the decimal point two places to the right to convert the decimal to a percent.)

6) 50 is what percent of 100?

$\frac{50}{100}=\frac{1}{2}$

$0.5=50%$  (Move the decimal point two places to the right to convert the decimal to a percent.)

7) An airline ticket on sale was $400. The original price of the ticket was$ 500. Find the discount.

• Hint: This is a problem of a percent decrease.

(move the decimal two places to the right and add the % sign)

8)  Movie ticket prices increased from $8 to$10 per ticket. What is the percent change?

• Hint: This is a problem of a percent decrease.

(move the decimal two places to the right and add the % sign)

## Cheat Sheet

• The change in percent change can be an increase or decrease.
• Percent Change =

## Blunder Areas

• Pay close attention to what is being asked. Then, read the information provided twice before deciding what rules to apply.
• Students often get the percent increase or decreased answer wrong.