A man covers 30 km of his journey at 10 km/h and the remaining 40 km at 20 km/h. Find his average speed for the whole journey. MCQ with Answer and Explanation
A man covers 30 km of his journey at 10 km/h and the remaining 40 km at 20 km/h. Find his average speed for the whole journey.
A. 15 km/h
B. 16 km/h
C. 12 km/h
D. 14 km/h
Answer: Option D
Solution (By JKSSB Mock Tests)
Total distance = 30 + 40 = 70 km. Time for first part = 30 / 10 = 3 hours. Time for second part = 40 / 20 = 2 hours. Total time = 5 hours. Average speed = 70 / 5 = 14 km/h.
A baseline boat hull can row 10 km/h in still water. If the river current tracks a velocity of 2 km/h, find the exact sector distance covered downstream by the boat hull in 30 minutes flat.
Explanation:
New speed = 8/9 of usual speed => New time = 9/8 of usual time. Difference = 1/8 of usual time = 12 minutes. Usual time = 12 * 8 = 96 minutes.
A train leaves a station at 4:00 PM and travels at an average speed of 60 km/h. Another train leaves the same station at 5:00 PM in the same direction at an average speed of 80 km/h. At what time will the second train catch up with the first train?
Explanation:
By 5:00 PM, the first train has traveled for 1 hour and covered 60 km. Relative speed = 80 - 60 = 20 km/h. Time needed to catch up = 60 / 20 = 3 hours. Catch up time = 5:00 PM + 3 hours = 8:00 PM.
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