A truck covers 60 km at 30 km/h and then another 100 km at 50 km/h. Find the overall average speed for the full transit. MCQ with Answer and Explanation
A truck covers 60 km at 30 km/h and then another 100 km at 50 km/h. Find the overall average speed for the full transit.
A. 38 km/h
B. 40 km/h
C. 42 km/h
D. 45 km/h
Answer: Option B
Solution (By JKExamLibrary)
Total distance = 60 + 100 = 160 km. Time for first leg = 60 / 30 = 2 hours. Time for second leg = 100 / 50 = 2 hours. Total time = 4 hours. Average speed = 160 / 4 = 40 km/h.
Explanation:
Let current speed be c. Upstream speed = 8 - c, Downstream speed = 8 + c. Given: 3 * (8 - c) = 8 + c => 24 - 3c = 8 + c => 4c = 16 => c = 4 km/h.
Explanation:
New speed = 4/5 of usual speed => New time = 5/4 of usual time. Difference = 1/4 of usual time = 15 minutes. Usual time = 15 * 4 = 60 minutes.
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