A boat covers 30 km downstream in 3 hours and the same distance upstream in 6 hours. Find the speed of the stream. MCQ with Answer and Explanation

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A boat covers 30 km downstream in 3 hours and the same distance upstream in 6 hours. Find the speed of the stream.

A. 3.0 km/h

B. 2.5 km/h

C. 2.0 km/h

D. 3.5 km/h

Answer: Option B

Solution (By JKSSB Mock Tests)

Downstream speed = 30 / 3 = 10 km/h. Upstream speed = 30 / 6 = 5 km/h. Speed of stream = (10 - 5) / 2 = 5 / 2 = 2.5 km/h.

This question belongs to: Maths Time Speed and Distance

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Question #1

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A student walks from his quarter block to the academy center at 4 km/h and arrives 8 minutes late. If he manages a pace of 5 km/h, he arrives 4 minutes early. Find the track distance.

A. 4.0 km

B. 3.5 km

C. 5.0 km

D. 4.5 km

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Correct Answer: Option A

Explanation:
Time difference = 8 - (-4) = 12 minutes = 10/60 = 1/5 hours. Let distance be d. d/4 - d/5 = 1/5 => d/20 = 1/5 => d = 4 km.

This question belongs to: Maths Time Speed and Distance

Question #2

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A walk at 5/6 of usual speed makes a person 10 minutes late. What is his usual time?

A. 60 minutes

B. 50 minutes

C. 40 minutes

D. 70 minutes

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Correct Answer: Option B

Explanation:
New Speed = 5/6 of usual speed => New Time = 6/5 of usual time. Difference = 1/5 * Usual Time = 10 minutes => Usual Time = 50 minutes.

This question belongs to: Maths Time Speed and Distance