JAMB 2023 Mathematics · Question 10

If a car runs at a constant speed and takes 4.5 hrs to run a distance of 225 km, what time will it take to run 150 km?

Options

A.2 hrs
B.4 hrs
C.3 hrs
D.1 hr

Answer: C. 3 hrs

Explanation written with AI and checked against the answer key

Analyze the question: The car moves at a constant speed, so time is directly proportional to distance. We know the time for 225 km and need the time for 150 km. Concept: Speed = Distance ÷ Time, so Time = Distance ÷ Speed. At constant speed, a shorter distance takes proportionally less time. Solution: Step 1: Find the speed. Speed = 225 ÷ 4.5 = 50 km/h Step 2: Find the time for 150 km. Time = 150 ÷ 50 = 3 hours Check using proportion: 150/225 = 2/3, and 2/3 × 4.5 = 3 hours ✓ Tip: When the speed is constant, find the speed first (Distance ÷ Time), then use it for the new distance. You can also scale by a ratio: 150 is 2/3 of 225, so the time is 2/3 of 4.5 hours.

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