# Boats and Streams ( 11 to 15 )

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Boats and Streams ( 11 to 15 ):

# APTITUDE QUESTIONS (BOATS AND STREAMS):

11. A boat can travel with a speed of 11 km/hr in still water. If the speed of the stream is 3 km/hr, find the time taken by the boat to go 70 km downstream.

A)    2 hours

B)    3 hours

C)    4 hours

D)    5 hours

E)    None of these

Explanation:

Speed downstream = (11 + 3) km/hr = 14 km/hr
Time taken to travel 68 km downstream = (70/14) hrs = 5 hrs.

12. Speed of a boat in standing water is 9 km/hr and the speed of the stream is 1.5 km/hr. A woman rows to a place at a distance of 105 km and comes back to the starting point. The total time taken by her is:

A)    16 hours

B)    18 hours

C)    20 hours

D)    24 hours

E)    None of these

Explanation:

Speed upstream = 7.5 km/hr; Speed downstream = 10.5 km/hr
∴ Total time taken = (10.5/7.5+10.5/10.5) hours = 24 hours

13. The speed of a boat in still water is 12 km/hr and the rate of current is 3km/hr. the distance traveled downstream in 12 minutes is:

A)    1.2 km

B)    3 km

C)    2.4 km

D)    3.6 km

E)    None of these

Explanation:

Speed downstream = (12 + 3) = 15 km/hr
Distance travelled = (15*12/60) km = 3 km

14. A man can row at 6 km/hr in still water. If the velocity of current is 1 km/hr and it takes him 1 hour to row to a place and come back, how far is the place?

A)    2.9 km

B)    2.5 km

C)    3 km

D)    3.6 km

E)    None of these

Explanation:

Speed downstream = (6 + 1) km/hr = 7 km/hr; Speed upstream = (6 -1) km/hr = 5 km/hr
Let the required distance be x km.
Then, x/7 + x/5 = 1  5x + 7x = 35  12x = 35  x = 2.9 km

15. A boat takes 20 hours for travelling downstream from point X to point Y and coming back to a point Z midway between X and Y. If the velocity of the stream is 4 km/hr and the speed of the boat in still water is 12 km/hr, what is the distance between X and Y?

A)    160 km

B)    180 km

C)    200 km

D)    220 km

E)    None of these

Explanation:

Speed downstream = (12 + 4) km/hr = 16 km/hr
Speed upstream = (12 – 4) = 8 km/hr
Let the distance between X and Y be a km. Then,
a/16 + ((a/2))/8 = 20  a/16 + a/16 = 20  a/8 = 20  a = 160 km