GMAT Quantitative: Ratios and Proportions 3 — Questions and Answers
Question 1: If 3:4 = 9:x, what is the value of x?
- 12 (Correct answer)
- 16
- 10
- 13
Correct answer: 12
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?
- 3 liters (Correct answer)
- 6 liters
- 15 liters
- 2 liters
Correct answer: 3 liters
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?
- 50 (Correct answer)
- 30
- 20
- 40
Correct answer: 50
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?
- 36 (Correct answer)
- 30
- 24
- 40
Correct answer: 36
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?
- 420 miles (Correct answer)
- 360 miles
- 400 miles
- 480 miles
Correct answer: 420 miles
Rate = 240/8 = 30 mpg, so 30 x 14 = 420 miles.
Question 6: Increasing a ratio's terms: if 5:8 is scaled so the first term becomes 35, what is the second?
- 56 (Correct answer)
- 48
- 40
- 64
Correct answer: 56
35/5 = 7 multiplier, so 8 x 7 = 56.
Question 7: If p:q = 3:5 and q:r = 2:7, what is p:r?
- 6:35 (Correct answer)
- 3:7
- 5:21
- 6:21
Correct answer: 6:35
Make q common: p:q = 6:10 and q:r = 10:35, so p:r = 6:35.
GMAT Quantitative: Ratios and Proportions 3
If 3:4 = 9:x, what is the value of x?