Ratios and Proportions

Front

What is a ratio?

Back

A ratio is a comparison of two quantities by division, showing how many times one value contains or is contained within the other.

Front

What is a proportion?

Back

A proportion is an equation that states that two ratios are equal.

Front

How do you calculate a percentage of a number?

Back

To calculate a percentage of a number, multiply the number by the percentage (in decimal form). For example, to find 15% of 400, calculate 400 x 0.15 = 60.

Front

If Sarah earns $400 and spends 15% on transportation, how much does she spend?

Back

$60

Front

What is the relationship between trucks and cars if there are 4 trucks for every 5 cars?

Back

The ratio of trucks to cars is 4:5.

Front

If 75 students represent 25% of the class, how do you find the total number of students?

Back

To find the total, divide the number of students by the percentage (in decimal form). Total = 75 / 0.25 = 300.

Front

What is the formula to find a part when given a percentage?

Back

Part = Total x Percentage (in decimal form).

Front

If 45% of a number n is 225, how do you find n?

Back

To find n, divide 225 by 0.45. n = 225 / 0.45 = 500.

Front

What is the first step in solving a proportion?

Back

Cross-multiply the two ratios.

Front

How do you express a ratio in simplest form?

Back

Divide both terms of the ratio by their greatest common divisor.