Ratios, Rates, & Percentages

what is it?

A ratio compares two numbers   (2 : 3). 

A proportion is an equation showing that two ratios are equal (2 : 3 = 4 : 6).

how to solve?

To find a missing number in a proportion, determine the "multiplier."

Example: If 1 bag of flour makes 12 cookies, how many bags for 36 cookies? 12 x 3 = 36, so multiply 1 bag by 3 to get 3 bags of flour.

what is it?

A rate compares two different units (e.g., $10 for 4 tickets).

A unit rate is the rate for one of something. This is the "secret weapon" for shopping!

how to solve?

Divide the first term by the second term. 

Example: If 5 applies cost $2.50, what is the price per apple? 

$2.50 ÷ 5 = $0.50 per apple.

what is it?

"Percent" literally means "per 100." 25% is just a ratio of 25 : 100 or the fraction 25/100.

how to find the percent of a number?

1. Multiply the number by the percent.

2. Divide by 100 (move the decimal point two places to the left).

• Example: Find 15% of 80.

  • 80 x 15 = 1200

  • 1200 ÷ 100 = $12.00