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Practice Question on boat and stream (aptitude)

Boat and stream

Question no. 1
A person can swim in still water at 4 km/h. If the speed of water is 2 km/h, how many hours will the man take to swim back against the current for 6 km.
looks_one 3
looks_two 4
looks_3 4.5
looks_4 None of these
Option looks_one 3
Solution :
Speed of swim = 4 km/hr
Speed of water = 2 km/ hr
against the water speed of swim = 2 km/hr
Time taken by man = distance/ speed = 6 / 2 = 3 hr

Question no. 2
A man can swim in still water at 4.5 km/h, buttakes thrice as long to swim upstream than downstream. The speed of the stream is
looks_one 2.25
looks_two 2
looks_3 3
looks_4 None of these
Option looks_one 2.25
Solution :
speed of swim = 4.5 km/hr
Time taken to downstream = x hr
Time taken to upstream = 3x hr
Speed of stream = z
distance of upstream = distance of downstream
(4.5 - z) * 3x = (4.5 + z )* x
( 4.5 - z )* 3 = 4.5 + z
4.5 + z = 13.5 - 3z
4z = 9
z = 2.25

Question no. 3
A boat takes 90 minutes less to travel 36 miles downstream 3. than to travel the same distance upstream. If the speed of the boat in still water is 10 mph, the speed of the stream is
looks_one 4 mph
looks_two 3 mph
looks_3 2.5 mph
looks_4 2 mph
option looks_4 2 mph
Solution :
let the speed of stream is y
let the time taken is x
A boat takes 90 minutes less to travel 36 miles downstream 3. than to travel the same distance upstream. If the speed of the boat in still water is 10 mph, the speed of the stream is

Question no. 4
A man takes twice as long to row a distance against the stream as to now the same distance in favour of the stream. The ratio of the speed of the boat (in still water) and the stream is
looks_one 2:1
looks_two 3:1
looks_3 3:2
looks_4 None of these
Option looks_two 3:1
Solution :
Speed of boat = x
speed of stream = y
Distance = D
A man takes twice as long to row a distance against the stream as to now the same distance in favour of the stream. The ratio of the speed of the boat (in still water) and the stream is options

Question no. 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?
looks_one 6
looks_two 8
looks_3 4
looks_4 None of these
Option looks_one 6
Solution :
Downstream :
D = 16 km
T = 2hr
Speed = Boat(x) + water(y)
x + y = D/T = 16/2 = 8
Upstream :
x- y = 16/4 = 4
x+ y = 8
x- y = 4
x = 6

Question no. 6
A man can swim with the stream at the rate of 3 kmph and against the Stream at the rate of 2 kmph. How long will it take him to Swim 7 km in still water?
looks_one 3 hr
looks_two 2.8 hr
looks_3 2.6 hr
looks_4 3.2 hr
Option looks_two 2.8 hr
Solution :
Swim with stream = speed of stream(y) + speed of man (x)
x + y = 3
swim against stream = speed of man(x) - speed of stream(y)
x - y = 2
2x = 5
x = 2.5 km/ hr
time to swim 7 km in still water = 7 / 2.5 = 2.8 hr

Question no. 7
If a man’s rate with the current is 12 km/hr. and the rate of the current is 1.5 km/hr, then man’s rate against the current is
looks_one 9
looks_two 6.75
looks_3 5.25
looks_4 None of these
Option looks_one 9
Solution :
Rate of current = 1.5 km/hr
Man's rate with current = rate of current + man's rate = 12
Man's rate = 12 - 1.5 = 10.5 km/hr
man's rate against the current = man's rate - rate of current = 10.5 - 1.5 = 9 km/hr

Question no. 8
A boy rows a boat against a stream flowing at 2 kmph for a distance of 9 km, and then turns round and rows back with the current. If the whole trip occupies 6 hours, find the boy’s rowing speed in still water.
looks_one 4 kmph
looks_two 2 kmph
looks_3 3 kmph
looks_4 5 kmph
Option looks_one 4 kmph
Solution :
Speed of boat against stream = x- y = 2 km/hr
distance = 9 km
time = 9/2 = 4.5
time taken to downstream = 6-4.5 = 1.5
x + y = 9 /1.5 = 6
x - y = 2
x + y = 6
x = 4

Question no. 9
A boat goes 24 km upstream and 28 km downstream in 6 hours. It goes 30km upstream and 21 km downstream in 6 hours and 30 minutes. The speed of the boat in still water is
looks_one 10 km/hr
looks_two 4 km/hr
looks_3 14 km/hr
looks_4 6 km/hr
Option looks_one 10 km/hr
Solution :
x is speed of boat
y is speed of stream
According to question
A boat goes 24 km upstream and 28 km downstream in 6 hours. It goes 30km upstream and 21 km downstream in 6 hours and 30 minutes. The speed of the boat in still water is

Question no. 10
A man rows to a place 48 km distant and back in 14 hours. He finds that he can row 4 km with the stream in the same time as 3 km against the stream. Find the rate of stream.
looks_one 1 km/ hr
looks_two 1.5 km/hr
looks_3 2 km/hr
looks_4 None of these
Option looks_one 1 km/ hr
Solution :
speed of man = x
speed of stream = y
According to question
A man rows to a place 48 km distant and back in 14 hours. He finds that he can row 4 km with the stream in the same time as 3 km against the stream. Find the rate of stream.

Question no. 11
A motor boat whose speed is 15 km/h in still water goes 30 km downstream and comes back in four and a half hours. The speed of the stream is
looks_one 6 km/hr
looks_two 7 km /hr
looks_3 8 km/ hr
looks_4 None of these
Option looks_4 None of these
Solution :
Speed of boat = 15 km/hr
According to question

Question no. 12
A boat takes 19 hours for travelling downstream from point A to point B and coming back to a point C midway between A and B. If the velocity of the stream is 4 kmph and the speed of the boat in still water is 14 kmph, what is the distance between A and B.
looks_one 160 km
looks_two 180 km
looks_3 200 km
looks_4 None of these
Option looks_two 180 km
Solution :
Let the distance between A and B = D
downstream speed = 14 + 4 = 18 kmph
upstream speed = 14 - 4 = 10 kmph
total time = 19 hr
according to question

Question no. 13
A boat goes 24 km upstream and 28 km downstream in 6 hours. It goes 30km upstream and 21 km downstream in 6 hours and 30 minutes. The speed of the stream is
looks_one 10 km/hr
looks_two 5 km /hr
looks_3 4 km /hr
looks_4 None of these
Option looks_one 10 km/hr
Solution :
x is speed of boat
y is speed of stream
According to question
A boat goes 24 km upstream and 28 km downstream in 6 hours. It goes 30km upstream and 21 km downstream in 6 hours and 30 minutes. The speed of the boat in still water is

Question no. 14
A small aeroplane can travel at 320km/h in still air. The wind is blowing at a constant speed of 40km/h. The total time for a journey against the wind is 135 minutes. What will be the time in minutes for the return journey with the wind ? (Ignore take off and landing for the airplane :
looks_one 94.5
looks_two 105
looks_3 108.125
looks_4 120
Option looks_two 105
Solution :
Speed of aeroplane = 320km/hr
speed of wind = 40 km/hr
Time taken against the wind = 135 min = 135/60 hr
Distance taken by aeroplane = ( 320 - 40 ) * 135/60 = 630 km
Time taken in return = 630 *60 / (320 + 40) = 105 minute

Question no. 15
A man can row 6 km/hr. in still water. It takes him twice as long to row up as to row down the river. Find the rate of stream
looks_one 2 km/hr
looks_two 4 km/hr
looks_3 6 km/hr
looks_4 None of these
Option looks_one 2 km/hr
Solution :
Speed of man = 6 km/hr
speed of stream = y km/hr
let the distance covered by man = D
Time taken in upstream = 2 times of time taken in downstream

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