GMAT Quantitative: Ratios and Proportions 3

Question 1

If 3:4 = 9:x, what is the value of x?

Accepted Answer

12

Answer

Cross-multiply: 3x = 36, so x = 12.

Question 2

A mixture has milk and water in ratio 5:1. If there are 18 liters total, how much water is there?

Accepted Answer

3 liters

Answer

Total parts = 6, each part = 18/6 = 3, water = 1 part = 3 liters.

Question 3

The ratio of a:b:c is 2:3:5 and their total is 100. What is c?

Accepted Answer

50

Answer

Total parts = 10, each part = 10, so c = 5 x 10 = 50.

Question 4

If y varies directly with x and y = 15 when x = 5, what is y when x = 12?

Accepted Answer

36

Answer

Constant k = 15/5 = 3, so y = 3 x 12 = 36.

Question 5

A car travels 240 miles on 8 gallons. At the same rate, how far on 14 gallons?

Accepted Answer

420 miles

Answer

Rate = 240/8 = 30 mpg, so 30 x 14 = 420 miles.

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