19
Q:

Rajesh rows in still water with a speed of 4.5 kmph to go to a certain place and comes back. Find his average speed for the whole journey, if the river is flowing with a speed of 1.5 kmph?

A) 2 kmph B) 4 kmph
C) 6 kmph D) 8 kmph

Answer:   B) 4 kmph



Explanation:

Let the distance in one direction = k kms

Speed in still water = 4.5 kmph

Speed of river = 1.5

Hence, speed in upstream = 4.5 - 1.5 = 3 kmph

Speed in downstream = 4.5 + 1.5 = 6 kmph

Time taken by Rajesh to row upwards = k/3 hrs

Time taken by Rajesh to row downwards = k/6 hrs

Now, required Average speed =Total distanceTotal speed = 2kk3 + k6 = 2k x 186k + 3k = 4 kmph 

 

Therefore, the average speed of the whole journey = 4kmph.

Q:

A boat covers a distance of 14 km upstream and 16 km downstream in 9 hours. It covers a distance of 12 km upstream and 40 km downstream in 11hours. What is the speed (in km/hr) of the boat in still water?

 

A)  5 B)  2
C)  3 D) 4
 
Answer & Explanation Answer: A)  5

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0 288
Q:

A man, rowing a boat, covers a distance of 16 km in two hours downstream. He covers half the distance in same amount of time when rowing upstream. Calculate the speed of the stream.

A) 4 kmph B) 2 kmph
C) 3 kmph D) 1 kmph
 
Answer & Explanation Answer: B) 2 kmph

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1 365
Q:

A boat covers 143 km upstream in 13 hours and the same distance downstream in 11 hours. What is the speed (in km/hr) of the boat in still water?

 

A) 10 B) 12
C) 14 D) 8
 
Answer & Explanation Answer: B) 12

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4 521
Q:

A boat cover row 12 km upstream in 4 hours and can cover the same distance downstream in 3 hours. What is the speed (in km/hr) of the boat in still water?

 

A) 3.5 B) 3
C) 2.5 D) 2
 
Answer & Explanation Answer: A) 3.5

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1 738
Q:

The upstream speed of the boat is 40 kmph and the speed of the boat in still water is 55 kmph. What is the downstream speed of the boat?

A) 75 kmph B) 70 kmph
C) 60 kmph D) 65 kmph
 
Answer & Explanation Answer: B) 70 kmph

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3 835
Q:

A boat goes 8 km upstream and 12 km downstream in 7hours. It goes 9 km upstream and 18 km downstream in 9 hours. What is the speed (in km/h) of the boat in still water?

 

A) 5 B) 4
C) 2 D) 3
 
Answer & Explanation Answer: D) 3

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3 849
Q:

A man can row his boat at a speed of speed of 4 kmph and he finds that the time taken rowing upstream is double to that taken downstream. Find the speed of the stream (in kmph).

A) 1.5 B) 1.3
C) 2 D) 1
 
Answer & Explanation Answer: B) 1.3

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9 898
Q:

Ramu can row 9 kmph in still water. It takes him twice as long to row up as to row down. Find the rate of stream.

A) 16 kmph B) 8 kmph
C) 3 kmph D) 9 kmph
 
Answer & Explanation Answer: B) 8 kmph

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2 697