Digital SATMath: Problem-Solving and Data AnalysisMedium
A city planner is analyzing traffic flow. On a particular road, 750 cars passed in 30 minutes. If this rate continues, how many cars would be expected to pass in 2 hours and 15 minutes?
- A2,250 cars
- B3,500 cars
- C3,750 cars
- D3,375 cars
Show answer & explanationAnswer & explanation
Correct answer: D. 3,375 cars
First, convert all times to minutes: 2 hours and 15 minutes = 120 + 15 = 135 minutes. The rate is 750 cars / 30 minutes = 25 cars per minute. Over 135 minutes, 25 cars/minute * 135 minutes = 3,375 cars.
Why the other options are wrong
- A. This results from multiplying 750 cars by 3, which implies 90 minutes (1.5 hours) instead of 2 hours 15 minutes.
- B. This might come from miscalculating the total time or the rate, or a simple arithmetic error.
- C. This might result from multiplying 750 cars by 5, implying 150 minutes (2.5 hours) of flow.
Rates and Unit Conversion
Rates describe how one quantity changes in relation to another, often requiring conversion of units to ensure consistency for calculations.
- Ensure units are consistent (e.g., all in minutes or hours).
- A rate is a ratio of two quantities with different units.
- Multiply the rate by the quantity of the independent variable to find the total.
Memory trick: Match units, find rate, then multiply for the new total time.