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The velocity of a boat in still water is 9 km/hr, and the speed of the stream is 2.5 km/hr. How much time will the boat take to go 9.1 km against the stream?

A.

2hr. 40min

B.

1 hr. 20min

C.

2hr. 48min

D.

1hr. 24min

Answer with explanation

Answer: Option DExplanation

Answer with the Explanation:

ATQ,

Speed of boat in still water (Sb) = 9km/hr Speed of stream (Sc) = 2.5km/hr Distance against the stream = 9.1 km

Note: against the steam = upstream

Now, apply the formula:

The speed of boat upstream = speed of boat – the speed of the stream

The speed of upstream = 9-2.5 = 6.5km/hr Now, time= Distance/speed Time = 9.1/6.5, or 7/5 Or, time = 1[2/5] Or, 1hr + (2/5)*60 = 1hr + 24minutes

Workspace

Michel can swim in still water at the rate of 6km per hour. After swimming in a stream, she realized that she takes twice the time to go upstream as she takes to go downstream. What is speed of the current?

A.

2 km/hr

B.

2.25 km/hr

C.

1.5 km/hr

D.

4 km/hr

Answer with explanation

Answer: Option AExplanation

Workspace

Guddi’s swimming speed in still water to the speed of river is 7:1. She swims 4.2 km up the river in just 14 min. How much time will Guddi take to swim 18.4 km down the river?

A.

12 minutes

B.

11 minutes

C.

46 minutes

D.

23 minutes

Answer with explanation

Answer: Option CExplanation

Workspace

The speed of a boat in still water is 5km/hr. If the speed of the boat against the stream is 3 km/hr, what is the speed of the stream?

A.

2 km/hr

B.

2.5 km/hr

C.

1 km/hr

D.

1.5 km/hr

Answer with explanation

Answer: Option AExplanation

**Answer with explanation:**

Let the speed of stream = X km/hr

Speed of boat = 5 km/hr

Speed upstream = 3km/hr

**Apply formula:** Speed upstream = speed of boat – speed of stream

∴ 3 = 5 – X

X = 5 – 3 = 2 km/hr

Workspace

A man can push upstream at 6km/hr and downstream at 10 km/hr. Discover man’s rate in still water and the rate of the momentum.

A.

7,9 km/hr

B.

6,8 km/hr

C.

4,5 km/hr

D.

5,6 km/hr

Answer with explanation

Answer: Option BExplanation

Speed upstream =6 km/hr` Speed downstream = 10 km/hr` Rate in still water = 1/2 (10-6) km/hr. = 6km/hr` Rate of the current = 1/2 (10+6) km/hr =8 km/hr

Workspace

If a man rows at 5 km/hr in still water and 3.5 km/hr against the current,then his rate along the current is

A.

6.5 km/hr

B.

8.5 km/hr

C.

4.25 km/hr

D.

6 km/hr

Answer with explanation

Answer: Option AExplanation

If The speed of boat or boatman in calm water is u kmph and The speed of water or stream is v kmph, then:In water, the speed along with stream= (u + v) kmph

Speed of current = 5 – 3.5 = 1.5 km/hr.

So the speed of man along the current = 5 + 1.5 = 6.5 km/hr

Workspace

A man can row 9 1/3 km/hr in still water and he finds that is thrice as much time to row u p than as to row down the same distance in river. The speed of the current is

A.

1 ¼ km/hr

B.

3 1/3 km/hr

C.

4 2/3 km/hr

D.

3 1/9 km/hr

Answer with explanation

Answer: Option CExplanation

Explanation:

Let Speed upstream = x km/hr

Speed downstream = 3x km/hr

Speed in still water = ½ (x+3x) km/hr = 2x km/hr

Speed of current = ½ (3x-x) km/hr = x km/hr

2x = 28/3 or x = 14/3 = 4 2/3 km/hr

Workspace

A motorboat in still water travels at a speed of 36 km/hr. It goes 56 km upstream in 1 hour 45 monutes. The time taken by it to cover the same distance down the stream will be

A.

2 hour 21 minutes

B.

2 hour 25 minutes

C.

1 hour 24 minutes

D.

3 hour

Answer with explanation

Answer: Option CExplanation

Workspace

A man rows downstream 32 km and 14 km upstream. If he takes 6 hours to cover each distance, then the velocity (in kmph) of the current is

A.

1.75 kmph

B.

3 kmph

C.

1.5 kmph

D.

2 kmph

Answer with explanation

Answer: Option CExplanation

Rate downstream = [32/6] kmph; Rate upstream = [14/6] kmph.

=> Velocity of current = 1/2[32/6 – 14/6] kmph

= 3/2 kmph

= 1.5 kmph

Workspace

For a motorboat that covers a certain distance downstream in 2 hours & returns in 3 hours, what would be its speed in still water if the speed of stream is 6 km/hr?

A.

15 km/hr

B.

9 km/hr

C.

36 km/hr

D.

30 km/hr

Answer with explanation

Answer: Option DExplanation

Workspace

A man can swim in still water at 4.5 km/h, but takes twice as long to swim upstream than downstream. The speed of the stream is?

A.

2.25

B.

7.5

C.

1.5

D.

3

Answer with explanation

Answer: Option CExplanation

Explanation:

M = 4.5

S = x

DS = 4.5 + x

US = 4.5 + x

4.5 + x = (4.5 – x)2

4.5 + x = 9 -2x

3x = 4.5

x = 1.5

Workspace

A person can swim in still water at 4 km/h. If the speed of water 2 km/h, how many hours will the man take to swim back against the current for 6km?

A.

4 (1/2)

B.

3

C.

4

D.

Insufficient data

Answer with explanation

Answer: Option BExplanation

Explanation:

M = 4

S = 2

US = 4 – 2 = 2

D = 6

T = 6/2 = 3

Workspace

A boatman goes 2 km against the current of the stream in 1 hour and goes 1 km along the current in 10 minutes. How long will it take to go 5 km in stationary water?

A.

40 minutes

B.

1 hr 30 min

C.

1 hour

D.

1 hr 15 min

Answer with explanation

Answer: Option DExplanation

Workspace

A boat can travel with a speed of 13 km/hr in still water. If the speed of the stream is 4 km/hr, find the time taken by the boat to go 68 km downstream

A.

2 hours

B.

4 hours

C.

3 hours

D.

5 hours

Answer with explanation

Answer: Option BExplanation

Solution:

Speed downstream

= (13 + 4) km/hr

= 17 km/hr

Time taken to travel 68 km downstream

= 6817

6817

hours

= 4 hours

Workspace

A man can row 9 (1/3) kmph in still water and finds that it takes him thrice as much time to row up than as to row down the same distance in the river. What is speed of the current ?

A.

3(1/2) km/hr

B.

5km/hr

C.

8 (3/2)km/hr

D.

4 (2/3) km/hr

Answer with explanation

Answer: Option DExplanation

Let man’s rate upstream be x km/hr. Then his rate downstream is 3 x km/hr

Given:

Speed in still water = 9 (1/3) = 28/3 km/hr

i.e, ½ (a+b) = 28/3 km/hr

½ (x+3x) = 28/3

2x = 28/3 x = 28/ 2 x 3 = 14/3 km/hr

rate upstream b = 14/3 km/hr and

rate downstream a = 14/3 x 3 = 14 km/hr

speed of the current = ½ (a-b) = ½ (14 – 14/3)

= ½ (42-14/3) = 28/6 = 4 (2/3) km/hr

Workspace

The speed of the boat in still water is 5 times that of current, it takes 1.1 hour to row to point B from point A downstream. The distance between point A and point B is 13.2 km. How much distance (in km) will it cover in 312 minutes upstrem?

A.

43.2

B.

48

C.

41.6

D.

44.8

Answer with explanation

Answer: Option CExplanation

Workspace

A boat takes half time in moving a certain distance downstream than upstream. What is the ratio between the rate in still water and rate of current?

A.

1 : 2

B.

3 : 1

C.

2 : 1

D.

1 : 3

Answer with explanation

Answer: Option BExplanation

Let the speed of the boat in still water be 4 km/hr and speed of the current be u km/hr.

Rate downstream = (u + v) km/hr.

Rate upstream = (u- v)km/hr

Let the distance covered in each case be x km.

Then 2x/(u + v) = x / (u – v)

=> 2 (u – v) = ( u + v)

=> u =3v

=> u/v =3/1

Workspace

A man rows ‘k’ km upstream and back again downstream to the same point in H hours. The speed of rowing in still water is s km/hr and the rate of stream is r km/hr. Then?

A.

(r + s) = kH / (r -s)

B.

(s^{2}-r^{2}) =2sk /H

C.

rs = kH

D.

None of the above

Answer with explanation

Answer: Option BExplanation

Time taken to cover total distance = H hrs.

Speed of upstream = s – r. Speed of downstream = s + r.

∴ k / (s + r) + k / (s – r) = H ⇒(s^{2}-r^{2}) =2sk /H

Workspace

A boat covers a certain distance downstream in 2 hour, while it comes back in 2 1/2 hours. If the speed of the stream be 5 kmph, what is the speed of the boat in still water?

A.

45 kmph

B.

35 kmph

C.

30 kmph

D.

40 kmph

Answer with explanation

Answer: Option AExplanation

Let the speed of the boat in still water be *x* kmph. Then,

Speed downstream = (*x* + 5) kmph,

Speed upstream = (*x* – 5) kmph.

(*x* + 5)*2 = (*x* – 5)*5/2

X = 45 kmph

Workspace

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