Boat & Stream - Quantitative Aptitude Questions and Answers
This section focuses on "Boat and Stream" of Quantitative Aptitude. These Multiple Choice Questions (mcq) should be practiced to improve the Quantitative Aptitude skills required for various interviews (campus interviews, walk-in interviews, company interviews), placements, entrance exams and other competitive examinations.
1. A boat takes 27 hrs to travel a distance upstream and takes 9hrs to travel the same distance downstream.
If the speed of the boat in still water is 12km/hr, then what is the velocity of the stream?
Explanation: Let the velocity of the stream be y km/hr
Then the speed of the downstream = (12 + y)km/hr
The speed of the upstream = (12 – y)km/hr
9 (12 + y) = 27 (12 – y)
108 + 9y = 324 – 27y
27y + 9y = 324 - 108
36y = 216
y = 6 km/hr
2. If a boy rows 8 km downstream in 6 hours and 4 km upstream in 4 hours then how long
will he take to cover 16 km in stationary (still) water?
Explanation: Distance covered in downstream = 8 km
Time taken in downstream = 6 hours.
Rate of downstream = 8/6=4/3 km/hr
Distance covered in upstream = 4 km
Time taken in upstream = 4hours.
Rate of upstream = 4/4 = 1 km/hr
Speed in still water = (1/2)(4/3+1) = 7/6km/hr
Time Taken to cover 16 km in still water = 16*6/7=14hrs (approximately)
3. A pedal boat goes 12km upstream and 14km downstream in 3hrs. It goes 15km upstream and 10.5km
downstream in 3 hrs 15mints. The speed of the boat in still water is:
Explanation: Let 'x' be the speed of the boat in still water
Let 'y' be the speed of the current.
Pedal boat will travel downstream at (x + y)km/hr and upstream (x – y)km/hr
Therefore 14/x +y + 12/ x –y = 3
10.5/(x+y) + 15/(x-y) = 13/4
70/(x+y) +60 /(x-y) =15 -->1
42 /(x+y) + 60/(x-y) = 13 -->2
From 1 and we get,
x+y = 14 ; x-y = 6
Therefore x= 10 ; y = 4
The speed of the pedalboat is 10 km/hr
4. A woman rows to a place 24km distant and come back in 7 hrs. She finds that she can
row 2km with the stream in the same time as 1.5km against the stream. The rate of the
Explanation: Suppose she move 2km downstream in x hrs
Then, speed of downstream = (2/x) km/hr
Speed of upstream = (1.5/x) km/hr
Therefore 24/(2/x) + 24/(1.5/x) = 7
12x + 16x = 7
X = (1/4)
So speed of downstream = 8km/hr and upstream = 6km/hr
Rate of the stream = (1/2) (8 - 6 )km/hr
= 1 km/hr
5. A fisherman rows to a place 24km distance and back in 7 hours. He finds that he can row 2km with the
stream in the same time 1.5 km against the stream.The rate of the stream is?
Explanation: Let be moves 2 km downstream in x Hours
Then in speed downstream = 2/x kmph
Speed in upstream = 1.5/x kmph
==> 24/2/X + 24/1.5/X = 7
Speed in downstream = 8 Kmph
Speed in upstream = 6 Kmph
Then the Rate of stream = 1/2 (8 - 6) = 1 Kmph
6. A boat man lakes 5hrs 30 mins to row a boat 30km downstream of a river and 4 hrs
15mints to cover a distance of 10km upstream. Find the speed of the river current in km/hr.
Explanation: Rate downstream = 30 / (11/2) km/hr
= 30 * 2 / 11 km/hr
= 60/11 km/hr
Rate upstream = 10 / (17/4)km/hr
= 10 * 4 / 17 km/hr
= 40 / 17 km/hr
Speed of current = 1 / 2 (a – b) km/hr
=1 / 2 (60 / 11 – 40 / 17)
= 1.5 km/hr (approx.)
7. Sakthi rows a boat at 4 km upstream in 1hour and 1 km downstream in 20 minutes.
How long will he take to reach 3.5km in still water?
Explanation: Upstream Speed = 4/1 = 4km/hr
Downstream Speed = 1/20 = 0.05 km/min
= 0.05*60 = 3 km/hr
Hence, speed of boat = 1/2( Upstream Speed + Downstream Speed)
= 1/2 (4+3)km/hr =3.5 km/hr
Thus, the time required to reach the distance of 3.5 km=DistanceCovered/Speed of boat
= 3.5/3.5km/hr =1 km/hr
8. A man goes 4km upstream of the stream in 2hr and goes 2km downstream of the stream in 20mints. How
long will it take to go 10km in stationary water?
Explanation: Rate downstream = (2/20 * 60) km/hr
= 6 km/hr
Rate upstream = 2 km/hr
Speed in still water = ½(6+2)km/hr
= 4 km/hr
Required time = distance / speed
= (10/4) hrs =(5/2)hrs
= 2hrs 30mins.
9. A motorboat running upstream takes 4 hrs 24 mins to cover a certain distance, while it takes 2hrs to cover
the same distance running downstream. What is the ratio between the speed of the boat and speed of the
water current respectively?
Explanation: Let the man's rate upstream be 'x' km/hr and downstream be 'y' km/hr
Then distance covered upstream by 4hrs 24mints = distance covered by downstream in 2hrs
(x * 4 2/5) = y *2
22x/5 = 2y
Y = 11x/5
Required ratio = (y+x/2) : (y –x/2)
= 16x/10 : 6x/10
= 16x : 6x
10. In one hour, a boat goes 13 km/hr in the direction of the stream and 7 km/hr against the direction of the stream. What will be the speed of the boat in still water?
Explanation: According to the formula,
Speed of a boat in still water = (1/2) (DownstreamSpeed + UpstreamSpeed)
Speed of boat in still water = (1/2) (13+7) = (1/2) × 20 = 10 km/hr