Boats and Streams Questions

Q:

A boatman can row 3 km against the stream in 20 minutes and return in 18 minutes. Find the rate of current ?

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

Explanation:

Speed in upstream = Distance / Time = 3 x 60/20 = 9 km/hr.

Speed in downstream = 3 x 60/18 = 10 km/hr

Rate of current = (10-9)/2 = 1/2 km/hr.

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29 15592
Q:

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 & Explanation Answer: D) 2 hrs

Explanation:

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.

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18 12907
Q:

A man rows his boat 60 km downstream and 30 km upstream taking 3 hrs each time. Find the speed of the stream ?

A) 5 kmph B) 10 kmph
C) 15 kmph D) 45 kmph
 
Answer & Explanation Answer: A) 5 kmph

Explanation:

Speed of the boat downstream  s=a/t= 60/3 = 20 kmph

Speed of the boat upstream s= d/t = 30/3= 10 kmph

 

Therefore,  The speed of the stream = speed of downstream - speed of upstream2=5 kmph

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33 12002
Q:

A boat running upstream takes 8 hours 48 minutes to cover a certain distance, while it takes 4 hours to cover the same distance running downstream. What is the ratio between the speed of the boat and speed of the water current respectively?

A) 7:4 B) 11:4
C) 4:7 D) 8:3
 
Answer & Explanation Answer: D) 8:3

Explanation:

Let the speed of the boat upstream be p kmph and that of downstream be q kmph

 

Time for upstream = 8 hrs 48 min = 845hrs

 

Time for downstream = 4 hrs

 

Distance in both the cases is same.

 

=> p x  845= q x 4

 

=> 44p/5 = 4q

 

=> q = 11p/5

 

 Now, the required ratio of Speed of boat : Speed of water current

 

q+p2:q-p2

 

=> (11p/5 + p)/2  : (11p/5 - p)/2

 

=> 8 : 3

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25 10988
Q:

A man swims downstream 72 km and upstream 45 km taking 9 hours each time; what is the speed of the current  ?

A) 1 kmph B) 3.2 kmph
C) 1.5 kmph D) 2 kmph
 
Answer & Explanation Answer: C) 1.5 kmph

Explanation:

72 --- 9
? ---- 1

=> Down Stream = 8

45 ---- 9 
? ---- 1

=> Up Stream = 5

Speed od current S = ?

S = (8 - 5)/2 = 1.5 kmph.

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16 10532
Q:

A man can row 8 kmh in still water. If the river is running at 2 kmh, it takes 4 hrs more upstream than to go downstream for the same distance. Then the distance is given by

A) 54 kms B) 32 kms
C) 45 kms D) 60 kms
 
Answer & Explanation Answer: D) 60 kms

Explanation:

Let the distance be d.

 d8-2-d8+2 = 4

 

=> 2d = 120 

 

=> d = 60 kms.

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23 10274
Q:

In one hour, a boat goes 12 km/hr along the stream and 6 km/hr against the stream. The speed of the boat in still water (in km/hr) is:

A) 9 B) 8
C) 7 D) 7.5
 
Answer & Explanation Answer: A) 9

Explanation:

Speed in still water = Average of Speed in Upstream and speed in Downstream

= 1/2 (12 + 6) kmph = 9 kmph.

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20 9237
Q:

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 & Explanation Answer: C) 21 km

Explanation:

Let the distance covered be D km. 

 D10+4+ D10-4 = 5

 D14+D6=5

 10D = 42 x 5 = 210

 

=> D = 21 km

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32 8878