100+ Boats and Streams Aptitude Questions and Answers Pdf - 2
Question: 6
A man can swim in still water at a rate of 4 km/hr. The width of the river is 1 km. How long will he take to cross the river straight, if the speed of the current is 3 km/hr?
(A) 10 min
(B) 12 min
(C) 15 min
(D) 18 min
Ans: C
Required time = Time taken to cover 1 km @ 4 kmph
= $$({1} / {4} × 60)$$ = 15 min.
Question: 7
Speed of a boat in standing water is 9 kmph and the speed of the stream is 1.5 kmph. A man rows to a place at a distance of 105 km and comes back to the starting point. The total time taken by him is
(A) 20 hours
(B) 22 hours
(C) 24 hours
(D) 32 hours
Ans: C
Speed upstream = 7.5 kmph.
Speed downstream = 10.5 kmph.
∴ Total time taken = $$({105} / {7.5} + {105} / {10.5})$$ hours = 24 hours.
Question: 8
In one hour, a boat goes 11 km along the stream and 5 km against the stream. The speed of the boat in still water (in km/hr) is
(A) 5
(B) 6
(C) 7
(D) 8
Ans: D
Speed in still water = $${1} / {2} × (11 + 5)$$
= $${1} / {2}$$ × (16) = 8 kmph.
Question: 9
A Boat goes 8 km in one hour along the stream and 2 km in one hour against the stream. The speed in km/hr of the stream is
(A) 1
(B) 2
(C) 3
(D) 4
Ans: C
Speed of the stream = $${1} / {2}(8 – 2)$$km/hr = 3 km/hr.
Question: 10
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) 20 km/hr
(B) 23 km/hr
(C) 27 km/hr
(D) 29 km/hr
Ans: B
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.
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