BANK & INSURANCE (BOAT AND STREAM) PART 1

Total Questions: 30

11. Speed of the boat in still water is 12km/hr and the speed of the stream is 4km/hr. then find the time taken(in hours) by boat to go 84 km and come back?

Correct Answer: (e) 15.75
Solution:Downstream speed = 12 + 4 = 16 km/hr

Upstream speed = 12 − 4 = 8 km/hr

Time taken to go 84 km and return back is

= 84/16 + 84/8

= 5.25 + 10.5 = 15.75

12. The speed of boat in still water is 8km/hr. A boatman goes a distance in downstream and return back. Speed of stream is 4km/hr. Then find average velocity (in km/hr)?

Correct Answer: (d) 6 
Solution:Let total distance is D

Downstream speed = 8 + 4 = 12 km/hr

Upstream speed = 8 − 4 = 4 km/hr

Average velocity = 2D / {(D/12) + (D/4)}

= 2×12/4

= 6 km/hr

13. A boat goes a certain distance downstream in 8 hours and returns back in 12 hours. If the speed of the stream is 5km/hr then find speed of the boat (in km/hr)?

Correct Answer: (c) 25
Solution:Let the distance is D km

Speed of boat is x km/hr

So according to the question,

D/x − 5 = 12 → (1) and

D/x + 5 = 8 → (2)

Dividing eq 1 from eq 2

(x + 5)/(x − 5) = 12/8 = 3/2

x = 25

So speed of boat is 25 km/hr

14. Speed of stream is 7km/hr and downstream speed is 35km/hr. Find the speed of upstream (in km/hr)?

Correct Answer: (b) 21 
Solution:Speed of boat is = 35 − 7 = 28 km/hr

So upstream speed = 28 − 7 = 21 km/hr

15. Speed of the boat in still water is 10km/hr and speed of stream is 3km/hr. then find the time taken (in hours) by boat in 49 km upstream?

Correct Answer: (a) 7 
Solution:Upstream speed = 10 − 3 = 7 km/hr

Time taken to go 49 km upstream is = 49/7 = 7 hour

16. A boat goes in 12 km upstream in 36 minutes. If the speed of the boat is 24km/hr then find the speed of the stream (in km/hr)?

Correct Answer: (e) 4
Solution:Upstream speed = boat speed − speed of stream

= 12/(36/60) = 20 km/hr

Speed of stream = 24 − 20 = 4 km/hr

17. A boat covers 2 km downstream in 30 minutes and covers 14 km upstream in 2 hours 20 min. find the speed of the boat in still water (in km/hr)?

Correct Answer: (d) 5 
Solution:Upstream speed = 2/(30/60) = 4 km/hr

Downstream speed = 14/(7/3) = 6 km

Speed of boat = (6 + 4)/2 = 10/2 = 5 km/hr

18. Speed of stream is 6 km/hr and downstream speed is 16km/hr. Find the ratio of upstream speed and downstream speed?

Correct Answer: (c) 1:4
Solution:Downstream speed = 16 km/hr

Speed of stream = 6 km/hr

Speed of boat = 16 − 6 = 10 km/hr

Upstream speed = 10 − 6 = 4 km/hr

Required ratio = 4:16 = 1:4

19. To go a certain distance in upstream a boat takes thrice as much time in going the same distance in downstream. Speed of the boat is 14km/hr then find speed of stream (in km/hr)?

Correct Answer: (b) 7
Solution:Let the distance D and speed of stream is x

So according to the question,

D/14 − x = 3x (D/14 + x)

42 − 3x = 14 + x

4x = 28 or, x = 7

Speed of stream = 7 km/hr

20. A boat goes a certain distance in downstream in 9 hours and returns back in 27 hours. If the speed of the boat is 12km/hr then find the distance (in km)?

Correct Answer: (a) 162 
Solution:Let the distance is D km

Speed of stream is x km/hr

So according to the question,

D/12 + x = 9 → (1)

and D/12 − x = 27 → (2)

Dividing eq 1 from eq 2

(12 − x)/(12 + x) = 1/3

Or, x = 6

D = 18×9 = 162 km