Hello Aspirants. Welcome to Online Quantitative Aptitude Section in AffairsCloud.com. Here we are creating question sample in Time and Distance- Boats and streams with Explanation, which is common for all the IBPS,SBI,SSC and other competitive exams. We have included Some questions that are repeatedly asked in bank exams !!!

1. If Nishu can swim downstream at 6kmph and upstream at 2kmph.What is his
speed in still water ?
A.5 km/hr
B.4 km/hr
C.8km/hr
D.7km/hr
Basic Formula:

If the speed downloadstream is a km/ hr and the speed upstream is b km/ hr
then Speed in still water is = ½ (a+b) km / hr [memory tool last 2 L cross and make +]            Explanation:
Given : speed downstream a = 6 km ph
Speed upstream b = 2kmph
Speed in still water = ½ (a+b) kmph
= ½ (6+2)
= 8/2 = 4kmph
speed in still water = 4kmph
2. Ashok can row upstream at 8kmph and downstream at 12kmph.What is the
speed of the stream ?
A.6km/hr
B.3km/h
C.2 km/hr
D.4km/hr
Basic Formula:
If the speed downstream is a kmph and the speed upstream is b kmph
then
Speed of the stream = ½ (a-b) kmph
Explanation:
Speed downstream a = 12kmph
Speed upstream b = 8 kmph
Speed of the stream = ½ (a-b) = ½ (12-8)
= 4/2 = 2 kmph
speed of the stream = 2kmph
3. A man rows 750m in 775 seconds against the stream and returns in 7
1/2 minutes. What is rowing speed in still water ?
A.4.7km/hr
B. 4km/hr
C.3.5km/hr
D.6km/hr
Basic Formula:
i) Speed in still water = ½ (a+b) kmph where ‘a’ is speed
downstream and ‘b’ is speed upstream
ii) a km / hr = a x 5/18 m /s
iii) a m/sec = a x 18/5 km/hr
Explanation:
Speed upstream ‘b’ = 750m / 775 sec = 30/31 m/sec
Speed downstream ‘a’ = 750 m/ (15/2)minutes [ 1min=60 sec] a = 750m/450 sec =5/3 m/sec
speed in still water = ½ (a+b)
= ½ (750/450 + 750/675 ) m /sec
= ½ (750/450 + 750/675 ) x 18/5 km/hr
= ½ (5/3 + 30/31) x 18/5 km/hr
= 4.7 km/hr
4. A man can row 9 (1/3) kmph in still water and finds that it takes him
thrice as much time to row up than as to row down the same distance in the
river. What is speed of the current ?
A. 5km/hr
B.3(1/2) km/hr
C.4 (2/3) km/hr
D.8 (3/2)km/hr
Basic Formula:
Speed of current = ½ (a-b) km/hr
Explanation:
Let man’s rate upstream be x km/hr. Then his rate downstream is 3 x km/hr
Given:
Speed in still water = 9 (1/3) = 28/3 km/hr
i.e, ½ (a+b) = 28/3 km/hr
½ (x+3x) = 28/3
2x = 28/3    x = 28/ 2 x 3 = 14/3 km/hr
rate upstream b = 14/3 km/hr and
rate downstream a = 14/3 x 3 = 14 km/hr
speed of the current = ½ (a-b) = ½ (14 – 14/3)
= ½ (42-14/3) = 28/6 = 4 (2/3) km/hr
5. Sham can row a boat at 10kmph in still water. IF the speed of the
stream is 6kmph, the time taken to row a distance of 80km down the stream
is
A.4 hours
B.5hours
C.3 hours
D.2 hours
Basic Formula:
Speed of stream = ½ (a-b) km/hr
Speed in still water = ½ (a+b) km/hr
Explanation:
Given:
Speed in still water, ½ (a+b) = 10 km/hr
a+b = 20 km/hr…………….(1)
speed of the stream, ½ (a-b) = 6km/hr
a-b = 12 km/hr …………….(2)
(1)+(2 ) we get 2a = 32
a = 16 km/hr
speed downstream =distance traveled / time taken
time taken = 80/16 = 5 hours
6. A boat takes 4hours for traveling downstream from point P to point
Q and coming back to point P upstream. If the velocity of the stream is 2km
ph and the speed of the boat in still water is 4kmph, what is the distance
between P and Q?
A.9 km
B.7 km
C.5 km
D.6km
Basic Formula:
Speed of stream = ½ (a-b) km/hr
Speed of still water = ½ (a+b) km/hr
Explanation:
Time taken by boat to travel upstream and downstream = 4 hours
Velocity of the stream, ½ (a-b) = 2km/hr
a-b = 4km/hr ……………….( 1)
velocity of the boat in still water = ½ (a+b) = 4km/hr
a+b = 8 km/hr ………………(2)
1 +2 we get a = 6 km/hr ,b = 2km/hr
let the distance between A and B be x km
x / 2 + x / 6 = 4
3x + x / 6 = 4  4x = 24 so,x = 6
distance between P and Q = 6km
7. Speed of a boat in standing water is 9kmph and the speed of the
stream is 1.5kmph. A man rows to a place at a distance of 10.5 km and
comes back to the starting point. Find the total time taken by him.
A.24 hours
B.16 hours
C.20 hours
D.15 hours
Basic Formula:
i. speed = distance traveled / time taken
ii. speed of the stream = ½ (a-b) km/hr
iii. speed in still water = ½ (a+b) km/hr
Explanation:
Speed in still water= ½ (a+b) = 9km ph
= a+b = 18 …………….1
speed of the stream = ½ (a-b) = 1.5 kmph
= a-b = 3 kmph…………2
solving 1 and 2 gives a = 10.5km/hr ; b=7.5 kmphr
Total time taken by him = 105/10.5 + 105/7.5 = 24 hours
8. A man rows to a place 48km distant and back in 14 hours. He finds
that he can row 4km with the stream in the same time as 3km against the
stream. Find the rate of the stream.
A.2 km/hr
B.1 km/hr
C.3 km/hr
D.3.5km/hr
Basic Formula:
Speed of the stream = ½ (a-b) km / hr
Speed = distance traveled / time taken
Explanation:
Suppose he moves 4km downstream in x hours
Then, downstream a= 4 / x km/hr
Speed upstream b = 3/ x km/hr
48 / (4 /x) + 48 / (3/x) = 14
12x + 16x = 14
x = 1/2
a=8 km/hr ,b = 6 km/hr
rate of stream = ½ (8 – 6 )
=  1 km/hr
9. There is road besides a river. Two friends started from a place P, moved to a shopping mall
situated at another place Q and then returned to P 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 P?
A. Both
B. Boater
C. Cyclist
D. None of these
Explanation:
The cyclist moves both ways at a speed of 12khr so average speed fo the
cyclist – 12 km/hr
boat sailor moves downstream at 10+4 = 14km/hr and upstream 10-
4 = 6km/hr
Average speed of the boat sailor = 2 x 14 x 6 / 14 +6 = 42/ 5 = 8.4km/hr
The average speed of cyclist is greater .so,cyclist comes first and return to
place P.
10. A this usual rowing rate, Mohit can travel 12 miles downstream in a certain river in 6
hours less than it takes him to travel the same distance upstream. But if he could double
his usual rowing rate for his 24 miles round trip, the downstream 12 miles would then
take only one hour less than the upstream 12 miles. What is the speed of the current in
miles per hour?
A.2.5m/hr
B.4 m/hr
C.8/3 m/hr
D. 5/3m/hr
Basic Formula:
Speed of the stream = ½ (a-b) km/hr
Explanation:
Let the speed in still water be x m/hr
Speed of stream be y m/hr
Then, speed upstream = x-y m/hr and
Speed downstream = x+y m/hr
12/x-y – 12 / x+y = 6 so,6 (x^2 – y^2) = 24 y
x^2 – y^2 = 4y
x^2 = y^2 + 4y…………..1
also
12/ 2x-y – 12/2x +y = 1 4x^2 – y^2 = 24y
x^2 = [24y + y^2] / 4 ……………….2
16y + 4y^2 = 24y + y2 [put X^2 value from 1] 3y^2 = 8 y so, y = 8/3
speed of the current = 8/3 m/hr = 2 (2/3) m/hr
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