A person row a boat 30 km downstream in 3 hours and returns upstream in 5 hours. Find the speed of the current. MCQ with Answer and Explanation

A person row a boat 30 km downstream in 3 hours and returns upstream in 5 hours. Find the speed of the current.
A. 2.0 km/h
B. 2.5 km/h
C. 3.0 km/h
D. 1.5 km/h
Answer: Option A
Solution (By JKSSB Mock Tests)
Downstream speed = 30 / 3 = 10 km/h. Upstream speed = 30 / 5 = 6 km/h. Speed of current = (10 - 6) / 2 = 2 km/h.

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Practice More Time Speed and Distance Questions

Question #1
Two trains 140 meters and 160 meters long are running at the speeds of 60 km/h and 40 km/h respectively in opposite directions on parallel tracks. What is the time taken by them to cross each other completely?
A. 9 seconds
B. 12 seconds
C. 10.8 seconds
D. 10 seconds

Correct Answer: Option C


Explanation:
Total distance to be covered = 140 + 160 = 300 meters. Relative speed = 60 + 40 = 100 km/h = 100 * (5/18) = 250/9 m/s. Time = Distance / Speed = 300 / (250/9) = 300 * 9 / 250 = 10.8 seconds.

This question belongs to: Maths Time Speed and Distance
Question #2
A train traveling at 60 km/h crosses a static tunnel in 18 seconds. If the length of the train is 120 meters, find the length of the tunnel.
A. 220 meters
B. 200 meters
C. 160 meters
D. 180 meters

Correct Answer: Option D


Explanation:
Speed of train = 60 * (5/18) = 50/3 m/s. Total distance covered in 18 seconds = (50/3) * 18 = 300 meters. Length of tunnel = 300 - 120 = 180 meters.

This question belongs to: Maths Time Speed and Distance
Question #3
Two athletes run a race of 400 meters. The ratio of their speeds is 4 : 5. If the faster runner completes the race, how far ahead is he from the slower runner at that instant?
A. 80 meters
B. 60 meters
C. 120 meters
D. 100 meters

Correct Answer: Option A


Explanation:
When the faster runner covers 5 parts = 400 meters, 1 part = 80 meters. In the same time, the slower runner covers 4 parts = 4 * 80 = 320 meters. Distance between them = 400 - 320 = 80 meters.

This question belongs to: Maths Time Speed and Distance