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A boatman can row 96 km downstream in 8 hr. If the speed of the current is 4 km/hr, then find in what time he will be able to cover 8 km upstream?

A.

1.5 hrs

B.

1 hrs

C.

2.5 hrs

D.

2 hrs

Answer with explanation

Answer: Option DExplanation

Speed in downstream = 96/8 = 12 kmph

Speed of current = 4 km/hr

Speed of the boatman in still water = 12 – 4 = 8 kmph

Speed in upstream = 8 – 4 = 4 kmph

Time taken to cover 8 km upstream = 8/4 = 2 hours.

Workspace

A.

5 km/hr

B.

3 km/hr

C.

7 km/hr

D.

9 km/hr

Answer with explanation

Answer: Option CExplanation

Let x be speed of u / s and y be the speed of d / s.

∴ (16/x) + (16/y) = (28/5) and 16/(y+2) + 16/(x-2) = 28/3

Solving these 2 equations, we get x = 4km/hr and y = 10km/hr

∴ speed of boat in still water = (4+10) / 2 = 7km/hr.

Workspace

A man rows to a place 40 km distant and come back in 9 hours. He finds that he can row 5 km with the stream in the same time as 4 km against the stream. The rate of the stream is:

A.

1 km/hr

B.

1.5 km/hr

C.

2 km/hr

D.

2.5 km/hr

Answer with explanation

Answer: Option AExplanation

Speed downstream = 5/x

Speed upstream = 4/x

40/(5/x) + 40/(4/x) = 9

X = ½

So, Speed downstream = 10 km/hr, Speed upstream = 8 km/hr.

Rate of the stream = 1/2 * 2 = 1 kmph

Workspace

The ratio of the speed of boat in still water to the speed of stream is 16 : 5. A boat goes 16.5 km in 45 minute upstream, find the time taken by boat to cover the distance of 17.5 km downstream.

A.

25 minutes

B.

30 minutes

C.

50 minutes

D.

45 minutes

Answer with explanation

Answer: Option AExplanation

Let the speed of boat in still water = 16x, speed of stream = 5x

Upstream speed = 16x – 5x = 11x

S = D/t

11x = (16.5 × 60)/45

x = 2

speed of boat in still water = 32 km/h, speed of stream = 10 km/h

Downstream speed = 32 + 10 = 42 km/h

Distance = 17.5 km

time = 17.5/42

= 5/12 hour

or( 5/12 )× 60 = 25 minutes

Workspace

Speed of a man in still water is 5 km/hr and the river is running at 3km/hr. The total time taken to go to a place and come back is 10 hours. What is the distance travelled?

A.

36 km

B.

32 km

C.

24 km

D.

10 km

Answer with explanation

Answer: Option BExplanation

Down speed= 5+3= 8

Up speed= 5-3=2

Let distance travelled = X

(X/8)+(X/2)= 10

X= 16 km

Total distance is 16+16=32

Workspace

A man goes down stream with a boat to some destination and returns upstream to his original place in 5 hours. If the speed of the boat in still water and the strean are 10km/hr and 14km/hr respectively, the distance of the destination from the string place is?

A.

16 km

B.

18 km

C.

21 km

D.

25 km

Answer with explanation

Answer: Option CExplanation

Workspace

A motorboat, whose speed in 15 km/hr in still water goes 30 km downstream and comes back in a total of 4 hours 30 minutes. The speed of the stream (in km/hr) is?

A.

2 km/hr

B.

3 km/hr

C.

4 km/hr

D.

5 km/hr

Answer with explanation

Answer: Option AExplanation

Let the speed of the stream be x km/hr. Then,

Speed downstream = (15 + x) km/hr,

Speed upstream = (15 – x) km/hr

So we know from question that it took 4(1/2)hrs to travel back to same point.

Workspace

A boat running downstream covers a distance of 16 km in 2 hours while for covering the same distance upstream, it takes 4 hours. What is the speed of the boat in still water?

A.

4 km/hr

B.

6 km/hr

C.

8 km/hr

D.

Data inadequate

Answer with explanation

Answer: Option BExplanation

Workspace

A man can row upstream 10 kmph and downstream 20 kmph. Find the man rate in still water and rate of the stream.

A.

9,5

B.

11,5

C.

15,5

D.

10,5

Answer with explanation

Answer: Option CExplanation

Please remember,

If a is rate downstream and b is rate upstream

Rate in still water = 1/2(a+b)

Rate of current = 1/2(a-b)

=> Rate in still water = 1/2(20+10) = 15 kmph

=> Rate of current = 1/2(20-10) = 5 kmph

Workspace

If sum of upstream and downstream speed of a boat is 82 kmph, and the boat travels 105 km. upstream in 3 hr, Find the time taken by boat to cover 126 km downstream.

A.

2.3 hrs

B.

2.7 hrs

C.

2.9 hrs

D.

2.5 hrs

Answer with explanation

Answer: Option BExplanation

Let Speed of boat in still water = b

Let Speed of still water = w

Then we know that,

Speed of Upstream = U = boat – water

Speed of Downstream = D = boat + water

Given, U + D = 82

b – w + b + w = 82

2b = 82

=> b = 41 kmph

From the given data,

41 – w = 105/3 = 35

w = 6 kmph

Now,

b + w = 126/t

=> 41 + 6 = 126/t

=> t = 126/47 = 2.68 hrs.

Workspace

If a boat goes 7 km upstream in 42 minutes and the speed of the stream is 3 kmph, then the speed of the boat in still water is

A.

15 kmph

B.

14 kmph

C.

13 kmph

D.

12 kmph

Answer with explanation

Answer: Option CExplanation

Rate upstream = (7/42)*60 kmh = 10 kmph.

Speed of stream = 3 kmph.

Let speed in sttil water is x km/hr

Then, speed upstream = (x —3) km/hr.

x-3 = 10 or x = 13 kmph

Workspace

A boat running downstream covers 24 km’s in 4 hours while for covering the same distance upstream it takes 6 hours whats the speed of the boat in still water?

A.

3.5km/hr

B.

5.5 km/hr

C.

6 km/hr

D.

None of these

Answer with explanation

Answer: Option DExplanation

Speed downstream = 24/4 km/hr = 6 km/hr

Speed upstream = 24/6 km/hr = 4 km/hr

Speed of the boat in still water = ½ (6 +4)km/hr = 5 km/hr

Workspace

A boat takes 4 hours for travelling downstream from point A to point B aild coming back to point A upstream. If the velocity of the stream is 2 kmph and the speed of the boat in still water is 4 kmph, what is the distance between A and B?

A.

B.

3 km

C.

6 km

D.

2 km

Answer with explanation

Answer: Option CExplanation

Let the distance between A and B be x km.

Speed downstream = 6 kmph, speed upstream = 2 kmph.

(x/6) + (x/2) = 4 4x = 24 hence x = 6

Distance AB = 6 km.

Workspace

A.

10(2/3)km/hr

B.

10.44 km/hr

C.

9.6 km/hr

D.

11.16 km/hr

Answer with explanation

Answer: Option CExplanation

4 km downstream is covered in 15 min. ∴ speed of downstream = 16 km/hr. So speed of upstream = 8km/hr. Total time taken for downstream journey = 15 min (given). Now total time taken for upstream journey = 8/8 = 1 hr = 60 min. Hence total time taken from A to B = 15 + 60 = 75 min. As average speed = Total distance /total time, so average speed from A to B = (12/75)*60 = 48/5 = 9.6kmph

Workspace

In one hour, a boat goes 11 km/hr along the stream and 5 km/hr against the stream. The speed of the boat in still water (in km/hr) is:

A.

3 km/hr

B.

5 km/hr

C.

8 km/hr

D.

9 km/hr

Answer with explanation

Answer: Option CExplanation

Speed in still water =1/2(11 + 5) kmph = 8 kmph.

Workspace

A man can row 30 km downstream and 20 km upstream in 4 hours. He can row 50km downstream and 60 km upstream in 9 hours. Find the speed of man in still water?

A.

15kmph

B.

10kmph

C.

12.5 kmph

D.

12kmph

Answer with explanation

Answer: Option CExplanation

let the speed upstream be: x km/hr and speed downstream be: y km/hr

now,

time=dist./speed.

so, 20/x+ 30/y=4 ………………….eqn(1)

and 50/x+ 60/y=9………………..eqn(2)

on solving both, we get :

x=10 km/hr and y=15 km/hr

now, speed of man in still water will be:

1/2*(y+x)= 1/2 * (15+10) = 25/2 = 12.5 km/hr.

rate of current will be : 1/2*(y-x) = 1/2 * (15-10) = 5/2 = 2.5 km/hr

Workspace

A boat covers 12 km upstream and 18km downstream in 3 hours while it covers 36km upstream and 24 km downstream in 6[1/2] hours, what is the velocity of the stream?

A.

1.5km/hr

B.

2km/hr

C.

3km/hr

D.

2.5km/hr

Answer with explanation

Answer: Option BExplanation

ATQ, Distance in upstream =12km

Distance in downstream = 18 km

Let the speed in upstream = y km/hr

And the speed in downstream = x km/hr

Now, apply the formula.

Time = Distance/ speed

Or, (18/x) + (12/y) = 3………….. (i)

And (24/x) + (36/y) = 13/2……… (ii)

Now, multiply equation i by 3 to equate both equations.

(54/x) + (36/y) = 9………… (iii)

(24/x) + (36/y) = 13/2…….. (iv)

Now subtract equation iii by iv.

30/x = 9-13/2

Or, 30/x = 5/2

Or, 5x=60, i.e., x = 12

Now, put the value of x in equation i

(18/12) + (12/y) = 3

Or, 3/2 + 12/y = 3

Or, 12/y = 3-3/2

Or, 12/y = 3/2

Or, y = 8km/hr

Now, velocity of stream = (x-y)/ 2

= (12-8)/ 2 = 2 km/hr.

Workspace

A man can swim at 5 km per hour velocity in still water. He takes 75 minutes to swim from position A to the position B and back in a river when it is flowing at 1 km per hour. The distance between A and B is?

A.

3 km

B.

8 km

C.

9 km

D.

15 km

Answer with explanation

Answer: Option AExplanation

Workspace

Speed of a boat in standing water is 9 kmph and the speed of the stream is 1.5 kmph. A man rows to a place at a distance of 105 km and comes back to the starting point. The total time taken by him is:

A.

18

B.

20

C.

24

D.

35

Answer with explanation

Answer: Option CExplanation

Speed upstream = 7.5 kmph.

Speed downstream = 10.5 kmph.

Total time taken =105/7.5 +105/10.5 hours = 24 hours.

Workspace

The speed of a boat in still water is 60kmph and the speed of the current is 20kmph. Find the speed downstream and upstream?

A.

35,25kmph

B.

80,40kmph

C.

40,60kmph

D.

50,55kmph

Answer with explanation

Answer: Option BExplanation

Speed downstream = 60 + 20 = 80 kmph

Speed upstream = 60 – 20 = 40 kmph

Workspace

A man takes twice as long to row a distance against the stream as to row the same distance in favour of the stream. The ratio of the speed of the boat (in still water) and the stream is:

A.

2:1

B.

3:1

C.

5:6

D.

9:5

Answer with explanation

Answer: Option BExplanation

Workspace

A.

16 km

B.

30 km

C.

42 km

D.

70 km

Answer with explanation

Answer: Option CExplanation

If a boat takes time ‘t’ hours more in upstream than to move downstream for the same distance, then the distance is given by,

Workspace

If athul rows 16 km upstream and 24 km down steam taking 4 hours each, then the speed of the

A.

1kmph

B.

2 kmph

C.

1.5 kmph

D.

12 kmph

Answer with explanation

Answer: Option AExplanation

Speed upstream = 16/4 = 4 kmph

Speed down stream = 24/4 = 6 kmph

Speed of stream = ½ (6-4) = 1 kmph

Workspace

A man’s speed with the current is 15 km/hr and the speed of the current is 2.5 km/hr. The man’s speed against the current is:

A.

8.5 km/hr

B.

10 km/hr

C.

12.5 km/hr

D.

9 km/hr

Answer with explanation

Answer: Option BExplanation

Man’s speed with the current = 15 km/hr

=> speed of the man + speed of the current = 15 km/hr

speed of the current is 2.5 km/hr

Hence, speed of the man = 15 – 2.5 = 12.5 km/hr

man’s speed against the current = speed of the man – speed of the current = 12.5 – 2.5 = 10 km/hr

Workspace

A boat covers a certain distance downstream in 1 hour, while it comes back in 1 hours. If the speed of the stream be 3 kmph, what is the speed of the boat in still water?

A.

13 kmph

B.

4 kmph

C.

14 kmph

D.

15 kmph

Answer with explanation

Answer: Option DExplanation

Workspace

A man rows to a place 48 km distant and come back in 14 hours. He finds that he can row 4 km with the stream in the same time as 3 km against the stream. The rate of the stream is:

A.

1 km/hr.

B.

2 km/hr.

C.

1.5 km/hr.

D.

2.5 km/hr.

Answer with explanation

Answer: Option AExplanation

Workspace

Speed of a boat in standing water is 14 kmph and the speed of the stream is 1.2 kmph. A man rows to a place at a distance of 4864 km and comes back to the starting point. The total time taken by him is:

A.

700 hours

B.

350 hours

C.

1400 hours

D.

1010 hours

Answer with explanation

Answer: Option AExplanation

Speed downstream = (14 + 1.2) = 15.2 kmph Speed upstream = (14 – 1.2) = 12.8 kmph Total time taken = 4864/ 15.2 + 4864/ 12.8 = 320 + 380 = 700 hours

Workspace

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