A commercial van covers 1/3 of a route sector distance at 20 km/h, 1/3 at 40 km/h and the final 1/3 segment at 40 km/h. Find the mean average speed. MCQ with Answer and Explanation
A commercial van covers 1/3 of a route sector distance at 20 km/h, 1/3 at 40 km/h and the final 1/3 segment at 40 km/h. Find the mean average speed.
A. 30 km/h
B. 28 km/h
C. 34 km/h
D. 32 km/h
Answer: Option A
Solution (By JKSSB Mock Tests)
Let each third segment distance be 40 km. Total sector distance = 120 km. Total time = 40/20 + 40/40 + 40/40 = 2 + 1 + 1 = 4 hours. Average speed across route = 120 / 4 = 30 km/h.
A person can row 10 km/h in still water. If it takes him exactly twice as long to row upstream as to row downstream over the same stretch, find the speed of the current.
Explanation:
Let speed of current be c km/h. Downstream speed = 10 + c, Upstream speed = 10 - c. Given: 2 * (10 - c) = 10 + c => 20 - 2c = 10 + c => 3c = 10 => c = 10/3 = 3.33 km/h.
Two delivery cars start from the same warehouse at the same time in identical directions. The first tracks a constant speed of 45 km/h and the second runs at 55 km/h. What is the distance between them after 2 hours 30 minutes?
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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