20 + Boats and Streams Questions and Answers | Quantitative Aptitude⬇️📝

2.5 hours
3 hours
4 hours
3.5 hours
4.5 hours

Answer: (3) 4 hours
Solution:
Downstream Speed = (13+4) km/hr = 17 km/hr
To travel 68 km downstream.
Time taken = 68/17 = 4 hours

8 km/hr
10 km/hr
14 km/hr
6 km/hr
Cannot Be Determined

Answer: (2) 10 km/hr
Solution:
According to the formula,
Speed of a boat in still water = ½ (DownstreamSpeed + UpstreamSpeed)
Speed of boat in still water = ½ (13+7) = ½ × 20 = 10 km/hr

5 km/hr
2 km/hr
4.5 km/hr
21 km/hr

Answer: (1) 5km/hr
Solution:
According to the formula,
Speed of the stream = ½ (Downstream Speed – Upstream Speed)
Speed of the stream = ½ (26-16) = ½ × 10 = 5 km/hr

2.5 km/hr
3.5 km/hr
4 km/hr
5 km/hr
3.25 km/hr

Answer: (4) 5 km/hr
Solution:
Let the speed of the stream be x km/hr
Upstream Speed = 15 + x
Downstream Speed = 15 – x
So, {30 / (15+x)} + {30 / (15-x)} = 4 ½ (4 hours 30 minutes)
⇒ {900 / (225-x2)} = 9/2
⇒ 9x² = 225
⇒x² = 25
⇒x = 5

1 hr 20 minutes
1 hr 30 minutes
1 hr 15 minutes
30 minutes
45 minutes

Answer: (3) 1 hr 15 minutes
Solution: 
Downstream = (1/10 × 60) = 6 km/hr
Upstream = 2 km/hr
Speed in still water = ½ (6+2) = 4 km/hr
So, the time is taken by the boat to go 5km in stationary water = 5/4 hrs = 1 ¼ hrs = 1 hr 15 minutes

4km/hr
6km/hr
8km/hr
10km/hr

Ans : B
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 

12km/hr
14km/hr
16km/hr
18km/hr

Ans : A
Explanation: Let rate of upstream be ‘x’km/hr and downstream be ‘y’ km/hr
Then, 12/x + 18/y = 3 –>1
18/x + 12/y =13/4 –>2
Adding 1 and 2 we get,
30/x + 30/y = 25/4
1/x + 1/y +=5/24 –>3
Subtracting 1 and 2 we get
1/x – 1/y = 1/24 –>4
Adding 3 and 4 we get,
2/x = 6/24 ; x= 8 ->5
Substitute 5 in 3 we get, y=12
Speed of upstream = 8 km/hr and downstream = 12 km/hr

8
14
22
16

Ans : B
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)

14/3
8/7
3/2
9/5

Explanation: Distance covered in downstream = 128km
Time taken in downstream = 24 hours.
Rate of downstream = distance / time = a = 128 km /24 hours = 16/3km/hr
Distance covered in upstream = 64km
Time taken in upstream = 16 hours.
Rate of upstream = distance / time = b = 64km /16hours = 4 km/hr.
Speed in still water = (a + b) / 2 = (1/2)(16/3+4) km/hr = (1/2)(28/3)km/hr
= 14/3km/hr

10
15
20
25

Ans : A
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

1kmph
1.5kmph
2.0kmph
2.5kmph

Ans : B
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.)

1/3kmph
2/3kmph
4/3kmph
5/3kmph

Ans : A
Explanation: Speed of the man (upstream) = (4 / 40 * 60) km/hr
= 6 km/hr
Speed of the man (downstream) = ( 4 / 36 * 60) km/hr
= (60 / 9)km/hr
= 20/3 km/h
Rate of the current = ½[downstream speed – upstream speed]
= (1/2) [ 20 / 3 – 6] km/hr
Rate of the current = 1/3 km/hr

1
2
3
4

Ans : A
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

8hr
3.33hr
5hr
4.33hr

Ans : B
Explanation: Upstream speed = x –y
Downstream speed = x + y
x– y = 30/10 = 3km/hr
Again x = 2y
Therefore x – y = 3
y= 3km/hr ; x = 6km/hr
Therefore x + y = 9 km/hr
Time during downstream = 30/9 = 3.33hrs

1.8 km/hr
3.33 km/hr
5 km/hr
33 km/hr
Solution- 5km/h
The ratio between downstream and upstream speed = 2:1
Let the upstream speed be 2x, then the speed downstream will be x
Speed is still water = (v+u) / 2 = (2x + x) / 2 = 3x/2 = 15 (given)
Hence, x = 10 km/h
Speed of stream = (v-u)/2 = (20-10)/2 = 5 km/h

5:6
3:7
7:9
8:3

Ans : D
Explanation: Let rate upstream = ‘x’ km/hr and
Rate downstream = ‘y’ km/hr
Then 80/x + 110/y = 26 —>1
60/x + 88/y = 20–>2
By solving 1 and 2
y= 11 ; x = 5
Rain in still water = (1/2) (11 + 5) km/hr = 8 km/hr
Rain of current = (1/2) (11 – 50) km/hr = 3 km/hr
The required answer is 8:3

8:3
5:2
3:7
2:4

Ans : A
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
= 8:3

1hr
2hr
3hr
4hr

Ans : D
Explanation: Downstream Speed = (13+4) km/hr = 17 km/hr
To travel 68 km downstream.
Time taken = 68/17 = 4 hours

10km/hr
20km/hr
30km/hr
40km/hr
Ans : A
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

1km/hr
5km/hr
3km/hr
9km/hr

Ans : B
Explanation: According to the formula,
Speed of the stream = (1/2)(Downstream Speed – Upstream Speed)
Speed of the stream = (1/2)(26-16) = (1/2) × 10 = 5 km/hr

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There are various exams like quantitative aptitude section of major government exams such as IBPS PO, IBPS Clerk, SBI PO, SBI Junior Associate, RRB Clerk, RRB Scale 1 Officer, SSC CGL, SSC CHSL, LIC Assistant, etc in which these types of questions actually comes in.

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