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SAT Math

Ratios, Rates, Proportions, and Units

Ratios, Rates, Proportions, and Units is a skill in the Problem-Solving and Data Analysis domain of the Digital SAT Math section. These are practice questions on it, and each answer choice comes with an explanation of why it is right or wrong.

11 questions. After every answer you’ll see why each choice is right or wrong, not just the one you picked.

Round length
Difficulty (none selected means all)

Sample questions

Open a question to see the answer choices and the correct answer.

A 3-D printer extrudes plastic filament at a constant rate of 2.4 grams per minute. At this rate, how many minutes will it take the printer to extrude 108 grams of filament?
  1. A. 45 ✓
  2. B. 90
  3. C. 259.2
  4. D. 4.5

Correct answer: A. Dividing the total mass by the rate gives 108 ÷ 2.4 = 45 minutes.

Brand A sells a 32-ounce container of oats for $5.44. Brand B sells a 20-ounce container of the same type of oats for $3.60. Based on cost per ounce, which brand offers the better value?
  1. A. Brand B, at $0.18 per ounce, is the better value.
  2. B. Brand A, at $0.17 per ounce, is the better value. ✓
  3. C. Brand B, at $0.20 per ounce, is the better value.
  4. D. Brand A, at $0.16 per ounce, is the better value.

Correct answer: B. Brand A costs $5.44 ÷ 32 = $0.17 per ounce, and Brand B costs $3.60 ÷ 20 = $0.18 per ounce; since $0.17 is less than $0.18, Brand A is the better value.

A conveyor belt moves boxes at a constant rate of 2.5 feet per second. At this rate, how many minutes does it take the belt to move a box 450 feet?
  1. A. 1.8
  2. B. 10,800
  3. C. 3 ✓
  4. D. 180

Correct answer: C. The time in seconds is 450 ÷ 2.5 = 180 seconds, and converting to minutes gives 180 ÷ 60 = 3 minutes.

A car travels at a constant speed of 54 miles per hour. What is this speed in feet per second? (1 mile = 5,280 feet)
  1. A. 79.2 ✓
  2. B. 39.6
  3. C. 158.4
  4. D. 792

Correct answer: A. Correct — converting gives 54 × 5,280 feet per hour, then dividing by 3,600 seconds per hour: (54 × 5,280)/3,600 = 79.2 feet per second.

A city has a population density of 850 people per square mile. If the city's total population is 2,975,000, what is the city's area, in square miles?
  1. A. 2,528,750,000
  2. B. 3,500 ✓
  3. C. 35,000
  4. D. 350

Correct answer: B. Correct — since density = population / area, area = population / density = 2,975,000 / 850 = 3,500 square miles.