100+ Boats and Streams Problems with Solutions Pdf - 1

Question: 1

A man can row upstream at 10 kmph and downstream at 18 kmph. Find the man’s rate in still water?

(A) 4 kmph

(B) 10 kmph

(C) 12 kmph

(D) 14 kmph

Ans: D

Speed of boatman in still water

= $${1} / {2} (Rate downstream + Rate upstream)$$

= $${1} / {2} (18 + 10)$$ = $${28} / {2}$$ = 14 kmph.

Question: 2

A man can row with the stream at 7 Km/h and against the stream at 3 Km/h. His speed in still water is

(A) 5 Km/h

(B) 7 Km/h

(C) 8 Km/h

(D) 9 Km/h

Ans: A

Speed of the man upstream = 7 Km/h.

Speed of the man downstream = 3 Km/h.

∴ Speed of the man in still water = $${1} / {2}$$ (Downstream speed + Upstream speed)

= $${1} / {2} (7 + 3)$$ = 5 Km/h.

Question: 3

A man can row upstream at 8 kmph and downstream at 13 kmph. The speed of the stream is

(A) 2 km / hr

(B) 2.5 km / hr

(C) 4.5 km / hr

(D) 5 km / hr

Ans: B

Speed of stream = $${1} / {2} (13 – 8)$$ kmph = 2.5 kmph.

Question: 4

A man rows, downstream 32 km upstream. If he takes 6 hours to cover each distance, then the velocity (in kmph) of the current is

(A) 1

(B) 1.5

(C) 1.5

(D) 2

Ans: C

Rate downstream = $$({32}/{6})$$ kmph

Rate upstream = $${14}/{6}$$ = 7 kmph.

∴ Velocity of current = $${1}/{2} ({32}/{6} – {14}/{6})$$ kmph = $${3}/{2}$$ kmph = 1.5 kmph.

Question: 5

A boat can travel with a speed of 13 km / hr in still water. If the speed of the stream is 4 km / hr, find the time taken by the boat to go 68 km downstream.

(A) 2 hours

(B) 3 hours

(C) 4 hours

(D) 5 hours

Ans: C

Speed downstream = (13 + 4) km/hr = 17 km/hr.

Time taken to travel 68 km downstream = $$({68} / {17})$$ hrs = 4 hrs.

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