# GED Math Extra Prep: Proportions

One or two questions on the GED Math test will ask you to find an unknown quantity of something, using a proportional relationship. The following practice questions ask you to do this by setting up a proportion where you are given three related values and you have to find the missing fourth value.

## Practice Questions

- On a sunny day, a tree casts a shadow that is 33 feet long. At the same time, a nearby 4-foot-tall mailbox casts a shadow that is 5.5 feet long. What is the height of the tree? Round your answer to the nearest foot.
**A.**24 feet

**B.**33 feet

**C.**38 feet

**D.**45 feet - Meg can swim 4 laps in 11 minutes. How long should she plan to practice if she needs to swim 10 laps, assuming her speed is constant?
**A.**4.4

**B.**15.7

**C.**22

**D.**27.5

## Answers and Explanations

- The correct answer is A.
Set up a proportion for the mailbox with the height as the numerator of the fraction and the shadow length as the denominator:

Substitute the given shadow length of the tree into the proportion and let

*x*equal the unknown height of the tree:Multiply both sides by 33 to solve for

*x:*Alternatively, you can solve the proportion by cross-multiplying and then dividing both sides by 5:

Choice (A) is the correct answer.

- The correct answer is D.
Set up a proportion with minutes as the numerator of the fraction and the number of laps as the denominator:

Substitute the given number of laps into the proportion, letting

*x*equal the unknown number of minutes:Multiply both sides by 10 to solve for

*x,*giving you*x*= 27.5.Alternatively, you can solve the proportion by cross-multiplying and then dividing both sides of the equation by 4:

Hence, Choice (D) is the correct answer.