BANK & INSURANCE (BOAT AND STREAM) PART 1

Total Questions: 30

1. Sum of the downstream speed and upstream speed of a boat is 36 Km/h. Speed of the boat in still water is 2 Km/h more than four times the speed of the stream. Find the total time taken by the boat to go 132 Km downstream and 56 Km upstream.

Correct Answer: (b) 10 hours 
Solution:Let, speed of the boat in still water = x km/h

And speed of the stream = y Km/h

x + y + x − y = 36

⇒ 2x = 36 ⇒ x = 36/2 ⇒ x = 18 Km/h

Now, 4y + 2 = 18

⇒ 4y = 18 − 2

⇒ 4y = 16 ⇒ y = 16/4 ⇒ y = 4 Km/h

Required time = 132/(18 + 4) + 56/(18 − 4)

= 132/22 + 56/14 = 6 + 4

= 10 hours

2. The ratio of speed of stream and boat is 1:7. If a boat covers 120 km upstream and downstream in 3.5 h, then find the sum of speed of boat and stream.

Correct Answer: (d) 80 kmph 
Solution:The ratio of speed of stream and boat = 1 : 7 (x, 7x)

[120/(7x − x)] + [120/(7x + x)] = 3.5

35/x = 3.5

x = 10

Required sum = 8 × 10 = 80 kmph

3. The upstream speed and downstream speed of the boat is 28 kmph and 36 kmph respectively. Find the time taken to cover the distance 224 km in still water.

Correct Answer: (b) 7 h
Solution:Speed of the boat in still water = (28 + 36)/2

= 32 kmph

Required time = 224/32 = 7 h

4. A fisherman goes 28 km along the stream and returning back to the same point in x hours. What is the value of x if the speed of the boat in still water is 12 km/hr and the speed of the stream is 2 km/hr?

Correct Answer: (d) 4.8 hrs 
Solution:Downstream speed of boat in River = 12 + 2

= 14 km/hr

Upstream speed of boat in River = 12 − 2 = 10 km/hr

So required time for the fisherman to return

= 28/14 + 28/10 = 2 + 2.8 = 4.8 hrs

5. If downstream speed is 20km/hr and upstream speed is 10km/hr. Find the speed of the stream(in km/hr)?

Correct Answer: (a) 5 
Solution:Upstream speed = boat speed − stream speed = 10

Downstream speed = boat speed + stream speed = 20

2×Speed of boat = 30

Speed of boat = 30/2 = 15

Speed of stream = 20 − 15 = 5

6. A boat goes a certain distance upstream in 6 hours and returns back in 4 hours. If the speed of the stream is 4 km/hr, find the distance(in km)?

Correct Answer: (e) 96
Solution:Let the distance is D km

Speed of boat is x km/hr

So according to the question,

D/x − 4 = 6 → (1) and

D/x + 4 = 4 → (2)

Dividing eq 1 from eq 2

(x + 4)/(x − 4) = 6/4 = 3/2

Or, x = 20

D = 16×6 = 96 km

7. A boat goes 20 km downstream in one hour and the same distance upstream in two hours. The speed of the boat(km/hr) in still water is?

Correct Answer: (d) 15 
Solution:Speed of boat is x

Speed of stream is y

So according to the question,

20/(x − y) = 2 Or x − y = 10 → (1)

20/(x + y) = 1 Or, x + y = 20 → (2)

From 1 and 2

we get 2x = 30

So, x = 15

Speed of boat is 15 km/hr

8. Ratio of downstream speed and upstream speed is 2:1. Then find ratio speed of boat and speed of stream?

Correct Answer: (c) 3:1
Solution:Let the downstream speed is 2x and upstream speed is x

So speed of boat is = 2x + x/2 = 3x/2

Speed of stream = 2x − x/2 = x/2

So required ratio = 3x/2 : x/2

= 3:1

9. A boat goes 75 km upstream in 3 hours and 60 km downstream in 1.5 hours. Find the speed of the boat in still water(in km/hr)?

Correct Answer: (b) 32.5 
Solution:Upstream speed = 75/3 = 25

Downstream speed = 60/1.5 = 40

Speed of boat = (40 + 25)/2 = 65/2 = 32.5 km/hr

10. If the speed of a boat in still water is 20km/hr and the speed of the current is 5km/hr. Then find the time taken by the boat to travel 100 km (in hours)?

Correct Answer: (a) 10.6 
Solution:Downstream speed = 20 + 5 = 25 km/hr

Upstream speed = 20 − 5 = 15 km/hr

Time taken to go 100 km and return back

= 100/25 + 100/15 = 4 + 6.6 = 10.6