100+ Boats and Streams Questions for Bank PO, SO, Clerk Exams - 1

Question: 1

There is a road beside a river. Two friends started from a place A, moved to a temple situated at another place B and then returned to A again. One of them moves on a cycle at a speed of 12 km/hr, while the other sails on a boat at a speed of 10 km/hr. If the river flows at the speed of 4 km/hr, which of the two friends will return to place A first?

(A) 8.2 km/hr

(B) 8.4 km/hr

(C) 8.6 km/hr

(D) 8.7 km/hr

Ans: B

Clearly, the eyelist, moves both ways at a speed of 12 km/hr.

So, average speed of the cyclist = 12 km/hr.

The boat sailor moves downstream @ (10 + 4) i.e. 14 km/hr and upstream = (10 – 4) i.e. 6 km/hr

So, average speed of the boat sailor = $$({2 × 14 × 6} / {14 + 6})$$ km/hr = $$({42}/ {5})$$

= 8.4 km/hr.

Question: 2

A boatman rows 1 km in 5 minutes, along the stream and 6 km in 1 hour against the stream. The speed of the stream is

(A) 2 kmph

(B) 3 kmph

(C) 6 kmph

(D) 7 kmph

Ans: B

Rate downstream = $$({1} /{5} × 60)$$kmph = 12 kmph;

Rate upstream = 6 kmph.

Speed of the stream = $${1}/{2}(12 – 6)$$kmph = 3 kmph.

Question: 3

A boat can travel 36 km upstream in 5 hours. If the speed of the stream is 2.4 kmph, how much time will the boat take to cover a distance of 78 km downstream?

(A) 5

(B) 5.5

(C) 6

(D) 6.5

Ans: D

Distance covered by a boat in 5 hours = 36 km

Rate upstream of boat = $${36}/{5}$$ = 7.2 kmph

Speed of stream = 2.4 kmph

∴ speed of boat in still water = (7.2 + 2.4) kmph = 9.6 kmph

Rate downstream in still water = (9.6 + 2.4) kmph = 12 kmph

∴ Time taken in covering 78 km distance = $${78}/{12}$$ = 6.5 hours.

Question: 4

A boat goes 13 km upstream in 39 minutes. The speed of stream is 3 km/hr. The speed of boat in still water is

(A) 23 km/hr

(B) 24 km/hr

(C) 26 km/hr

(D) 28 km/hr

Ans: A

Speed of the boat upstream = $${13 × 60} / {39}$$ = 20 km/hr

Speed of the stream = 3 km/hr

Let, the speed of the boat in still water = x km/hr, we have, x – 3 = 20.

∴ x = 20 + 3 = 23 km/hr.

Question: 5

A boat running downstream covers a distance of 16 km in 2 hours while for covering the same distance upstream, it takes 4 hours. What is the speed of the boat in still water?

(A) 4 km /hr

(B) 6 km /hr

(C) 7 km /hr

(D) 8 km /hr

Ans: B

Rate downstream =$$({16}/{2})$$ kmph = 8 kmph;

Rate upstream = $$({16}/{4})$$ kmph = 4 kmph.

∴ Speed in still water = $${1}/{2}(8 + 4)$$ kmph = 6 kmph.

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