Difficulty: Medium
Correct Answer: 120 km/h
Explanation:
The train is 50% faster than the car, but it has stoppage time. Equal arrival times imply the car’s running time equals the train’s running time plus stoppage.
Given data
Step-by-step calculation
Car time = 75 / cTrain running time = 75 / (1.5c)Car time = Train running time + stoppage75 / c = 75 / (1.5c) + 25/12075 / c − 50 / c = 25/12025 / c = 25/120c = 120 km/h
Verification
Car time = 75 / 120 = 0.625 hTrain run time = 75 / 180 = 0.4167 h; add 0.2083 h stoppage = 0.625 h (matches)
Common pitfalls
Don’t forget to convert 12.5 minutes to hours, and don’t set distances unequal—the distance is the same for both.
Final Answer
120 km/h
Discussion & Comments