Bluebook SAT Test Ratios, Rates, Proportional Relationships, and Units 7 โ Questions and Answers
Question 1: A hose fills a 2,400-gallon pool in 8 hours. A second hose fills it in 12 hours. How many hours will it take both hoses together to fill the pool?
- 3.6 hr
- 4.0 hr
- 4.8 hr (Correct answer)
- 5.2 hr
Correct answer: 4.8 hr
Combined rate = 1/8 + 1/12 = 5/24 pools/hr; time = 24/5 = 4.8 hours.
Question 2: A wheel has a radius of 35 cm. How many full rotations does the wheel make when it travels 440 meters? (Use ฯ โ 22/7)
- 150
- 180
- 200 (Correct answer)
- 220
Correct answer: 200
Circumference = 2 ร (22/7) ร 35 = 220 cm = 2.2 m; rotations = 440 รท 2.2 = 200.
Question 3: A recipe requires 2.5 cups of milk for every 3 cups of flour. If a chef has 9 cups of flour, how many cups of milk are needed?
- 6.5
- 7.0
- 7.5 (Correct answer)
- 8.0
Correct answer: 7.5
Milk = (2.5/3) ร 9 = 7.5 cups.
Question 4: A town's population grows at a constant rate. Its population was 15,000 in 2010 and 18,000 in 2015. What will the population be in 2020 at this rate?
- 19,500
- 20,500
- 21,000 (Correct answer)
- 22,000
Correct answer: 21,000
Growth = 3,000 per 5 years; 2020 population = 18,000 + 3,000 = 21,000.
Question 5: A metal pipe is 4 meters long and weighs 24 kg. What is the weight, in kg, of a pipe of the same material that is 6.5 meters long?
- 36.5 kg
- 38 kg
- 39 kg (Correct answer)
- 40.5 kg
Correct answer: 39 kg
Weight per meter = 24 รท 4 = 6 kg/m; weight = 6 ร 6.5 = 39 kg.
Question 6: In a class, 60% of students passed a math test and 80% passed an English test. If 30 students passed both and every student passed at least one test, how many students are in the class?
- 60
- 75 (Correct answer)
- 90
- 100
Correct answer: 75
By inclusion-exclusion: (0.60 + 0.80)n โ 30 = n โ 1.40n โ 30 = n โ 0.40n = 30 โ n = 75.
Question 7: A substance's speed of sound is 340 m/s. How long, in milliseconds, does it take sound to travel 85 meters? (1 s = 1,000 ms)
- 200 ms
- 225 ms
- 250 ms (Correct answer)
- 275 ms
Correct answer: 250 ms
Time = 85 รท 340 = 0.25 s = 250 ms.
Bluebook SAT Test Ratios, Rates, Proportional Relationships, and Units 7
A hose fills a 2,400-gallon pool in 8 hours.
A second hose fills it in 12 hours.
How many hours will it take both hoses together to fill the pool?