Proportions

Front

What is a proportion?

Back

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

Front

How do you solve a proportion?

Back

To solve a proportion, cross-multiply the terms and set the products equal to each other.

Front

What does it mean for two quantities to vary directly?

Back

Two quantities vary directly if one quantity is a constant multiple of the other.

Front

If a car travels 280 miles in 7 hours, what is its speed in miles per hour?

Back

Speed = Distance/Time = 280 miles / 7 hours = 40 miles per hour.

Front

If a car travels at a speed of 40 miles per hour, how far will it travel in 12 hours?

Back

Distance = Speed x Time = 40 miles/hour x 12 hours = 480 miles.

Front

What is the formula for finding the expected number of items in a population based on a sample?

Back

Expected number = (Sample size / Total population) x Estimated total population.

Front

If John caught 14 trout out of 50 fish, what is the proportion of trout?

Back

Proportion of trout = 14/50 = 0.28 or 28%.

Front

How do you determine if two ratios form a proportion?

Back

Two ratios form a proportion if their cross products are equal.

Front

What is the cross product of the ratios 3/6 and x/12?

Back

Cross product = 3 * 12 = 36 and 6 * x = 6x. Set 36 = 6x to solve for x.

Front

If hamburger sells for 3 pounds for $6, what is the cost per pound?

Back

Cost per pound = $6 / 3 pounds = $2 per pound.