Ratios/Rates/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 rate?

Back

A rate is a specific kind of ratio that compares two quantities with different units, such as speed (miles per hour) or price per item.

Front

What is a proportion?

Back

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

Front

How do you calculate the unit cost?

Back

To calculate the unit cost, divide the total cost by the number of units. For example, if 15 pizzas cost $97.50, the unit cost is $97.50 ÷ 15 = $6.50 per pizza.

Front

Which is a better buy: 12-pack of soda for $3.50 or 6-pack for $1.80?

Back

To find the better buy, calculate the cost per item. 12-pack: $3.50 ÷ 12 = $0.29 per soda; 6-pack: $1.80 ÷ 6 = $0.30 per soda. The 12-pack is the better buy.

Front

If Maya earns $10 an hour, how many hours to earn $150?

Back

To find the hours, divide the total amount by the hourly wage: $150 ÷ $10 = 15 hours.

Front

How do you find the cost of one item from a total cost?

Back

To find the cost of one item, divide the total cost by the number of items. For example, if 20 adult tickets cost $250, the cost per ticket is $250 ÷ 20 = $12.50.

Front

If Ernie travels 195 miles in 3 hours, how far will he travel in 5 hours?

Back

First, find the speed: 195 miles ÷ 3 hours = 65 miles per hour. Then, multiply by 5 hours: 65 miles/hour × 5 hours = 325 miles.

Front

What is the formula for calculating speed?

Back

Speed = Distance ÷ Time.

Front

What does it mean if two ratios are in proportion?

Back

If two ratios are in proportion, it means that the cross products are equal. For example, if a/b = c/d, then a*d = b*c.