Boats & Streams Questions for RRB NTPC PDF

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Boats & Streams Questions for RRB NTPC PDF
Boats & Streams Questions for RRB NTPC PDF

Boats & Streams Questions for RRB NTPC PDF

Download RRB NTPC Boats & Streams Questions and Answers PDF. Top 15 RRB NTPC Boats & Streams questions based on asked questions in previous exam papers very important for the Railway NTPC exam.

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Question 1: Find the difference in time taken by the boat travelling at 25 km/hr to cover 60 while travelling upstream and downstream. Speed of the stream is 5 km/hr.

a) 60 minutes

b) 30 minutes

c) 90 minutes

d) 40 minutes

Question 2: A man can row 24km/hr in still water. It takes twice as long to travel any distance upstream as compared to the same distance downstream. Find the speed of the stream.

a) 12

b) 10

c) 8

d) 6

Question 3: Find the speed of the boat if it takes 3 hours to travel a distance of 90km upstream and the speed of the stream is 4 km/hr?

a) 30km/hr

b) 34km/hr

c) 38km/hr

d) 42km.hr

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Question 4: Find the distance covered by the boat upstream if it travels for 2 hours. Speed of the stream is 7km/hr and that of the boat is 57km/hr.

a) 128km

b) 100km

c) 110km

d) 120km

Question 5: A boat travels 60km upstream and comes back in 8 hours. What is the speed of the boat if the speed of the stream is 4 km/hr?

a) 16km/hr

b) 20km/hr

c) 12km/hr

d) 18km/hr

Question 6: What is the time taken by a boat to travel 120km upstream and back to the starting point if the speed of the boat is 25km/hr and the speed of the stream is 5km/hr.

a) 8 hrs

b) 12 hrs

c) 14 hrs

d) 10 hrs

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Question 7: The rates upstream and downstream of a swimmer are 10 kmph and 13 kmph respectively. The speed of current is

a) 3 kmph

b) 1.5 kmph

c) 11.5 kmph

d) None of these

Question 8: A man rows upstream 16km and down stream 28km, taking 5 hour each time, the velocity of the current

a) 2.4 km/hr

b) 1.2 km/hr

c) 3.6 km/hr

d) 1.8 km/hr

Question 9: A boat goes at a speed of 30 kmph in still water. What time does it take to travel 50 kms upstream and then 70 kms downstream in water of speed 5 kmph?

a) 2 hours

b) 4 hours

c) 6 hours

d) 8 hours

Question 10: A boat can travel 27 km in one hour in still water and travels the same distance against the stream in 90 minutes. How much time will the boat take to travel 90 km in the direction of the stream?

a) 4 hours

b) 4.25 hours

c) 2.5 hours

d) 3.5 hours

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Question 11: Speed of a boat upstream is 3kmph and while running downstream it has travelled 49km in 7hrs.Find the speed of the river ?

a) 2kmph

b) 3kmph

c) 5kmph

d) 7kmph

Question 12: Speed of a boat during upstream is 3kmph and during downstream, it travelled 49km in 7hrs.Find the speed of the boat in still water ?

a) 2kmph

b) 3kmph

c) 5kmph

d) 7kmph

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Question 13: Find the speed of a boat in still water, which took 2 hrs to travel a distance during upstream and 6 hrs to travel the same distance during downstream, if speed of stream is 2 kmph ?

a) 2 kmph

b) 3 kmph

c) 4 kmph

d) 5 kmph

Question 14: Find the speed of the river, if a boat took 12 hrs to travel upstream and 4 hrs to travel downstream. Assume speed of the boat in still water is 4kmph ?

a) 0.5 kmph

b) 1 kmph

c) 1.5 kmph

d) 2 kmph

Question 15: Find the distance covered by a boat in 30 mins during downstream, if its speed in still water is 7 kmph and speed of the stream is 5 kmph ?

a) 6 km

b) 7 km

c) 8 km

d) 9 km

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Answers & Solutions:

1) Answer (A)

Speed of the boat upstream = (25-5)km/hr = 20 km/hr
Speed of the boat downstream = (25+5)km/hr = 30 km/hr
Distance = 60 km
Time taken upstream = 60/20 = 3 hours
Time taken downstream = 60/30 = 2 hours
Difference in time taken = 3-2 = 1 hour

2) Answer (C)

Since it takes twice as long in upstream,
Net speed in Upstream = x
Net speed in downstream = 2x
Let the speed of stream be y
24-y = x
24+y = 2x
24+y = 2(24-y)
3y = 24
y = 8

3) Answer (B)

Let the speed of the boat be x.

Speed of the boat Upstream = x-4

90/(x-4) = 3

x = 34km/hr

4) Answer (B)

Speed of the boat upstream = (57-7)km/hr = 50km/hr
Time = 2 hours
Distance = 50*2 = 100km

5) Answer (A)

Distance = 60km
Let speed of the boat be x
Speed of the boat upstream = (x-4) km/hr
Speed of the boat downstream = (x+4)km/hr
Total time = 8 hours
$\frac{60}{x-4} + \frac{60}{x+4} = 8$
$x^2-15x-16 = 0$
$x^2-16x+x-16 = 0$
(x+1)(x-16) = 0
x = -1 or +16

As speed cannot be negative, x=16km/hr

6) Answer (D)

Speed of the boat upstream = 25-5 = 20km/hr
Speed of the boat downstream = 25+5 = 30km/hr
Time take =$\frac{120}{30}+\frac{120}{20}$ = 4+6 hrs = 10 hrs

7) Answer (B)

Let the speed of the current be c

Speed of the swimmer = s

s + c = 13 ….. (1)

s – c = 10 …….(2)

Subtracting (2) from (1), we get 2c = 3 or c = 1.5

8) Answer (B)

Let the man’s speed be m and the speed of current be c

Time taken in downstream = $ \frac{28}{m+c}$ = 5

Time taken in upsteam = $ \frac{16}{m-c}$ = 5

Subtracting second equation from first equation, we get 10 c = 12 or c = 1.2

9) Answer (B)

The relative speed of the boat in upstream = 30 – 5 = 25 kmph
Distance = 50 kms
Time = 50 / 25 = 2 hours.

Relative speed in downstream = 30 + 5 = 35 kmph
Distance = 70 kms
Time = 70/35 = 2 hours.

Total time = 2 + 2 = 4 hours.

10) Answer (C)

Let ‘s’ be the speed of the boat and ‘w’ be the speed of the stream.
We have, s = 27 km/hr and $\frac{27}{s-w} = 1.5 $ hour
So s – w = 18 so w = 9 km/hr
We get, $\frac{90}{18+9} = 2.5$ hour
Hence, option C is the right choice.

11) Answer (A)

Speed of boat in still water = x say

Speed of stream = y say

During upstream, speed = x-y = 3kmph ——-(1)

During downstream, speed = x+y = 49/7 = 7 kmph ——-(2)

On solving (1) & (2)

x = 5 kmph & y = 2 kmph

So the answer is option A.

12) Answer (C)

Let x, y are the speeds of boat and river.

Speed during upstream = x-y = 3 ——-(1)

speed during downstream = x+y = 49/7 = 7——-(2)

On solving (1) & (2)

x = 5 kmph y = 2 kmph

So the answer is option C.

13) Answer (C)

Let x be the speed of the boat in still water,

During upstream, speed $S_1=x-2$

During downstream, speed $S_2=x+2$

$S_1t_1=S_2t_2$

$(x-2)(6) = (x+2)(2)$

$6x-12 = 2x+4$

$4x = 16$

$x = 4 kmph$

So the answer is option C.

14) Answer (D)

Let x be the speed of the river.

During upstream, speed = 4-x kmph , time = 12hrs

During downstream, speed = 4+x kmph, time = 4hrs

(4-x)(12) = (4+x)(4)

48-12x = 16+4x

32 = 16x

x = 2

So the answer is option D.

15) Answer (A)

Relative speed during downstream = 7+5 = 12 kmph

Time = 30 mins = 1/2 hr = 0.5 hrs

Distance = Speed*Time = 12*0.5 = 6 km

So the answer is option A.

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