Boats and Streams :(31) MCQs with Answers

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1.

A man can row downstream at the rate of 24 Kmph and upstream at 7 Kmph. Find the man’s rate in still water and rate of current?

   A.) 15.5 Kmph, 8.5 Kmph
   B.) 17 Kmph, 8.5 Kmph
   C.) 814 Kmph, 7 Kmph
   D.) None of these

Answer: Option 'A'

Rate of still water = 1/2 (down stream + upstream) 
= 1/2 (24 + 7) = 15.5 Kmph 
rate of current = 1/2 (down stream - upstream) 
= 1/2 (24 - 7) = 1/2 (17) = 8.5 kmph

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2.

A man can row 24 kmph in still water. It takes him thrice as long to row up as to row down the river. Find the rate of the stream? 

   A.) 4 kmph
   B.) 12 kmph
   C.) 6 kmph
   D.) 1 kmph

Answer: Option 'B'

Let man's rate upsteam be X kmph 
Then his rate of downstream = 3X kmph 
Rate still water = 1/2 (3X + X) = 2X 
2X = 24 
X = 12 
Rate of upstream = 12 
Rate of downstream = 36 
Rate of stream 1/2 ( 36 - 12) = 12 kmph

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3.

In a stream running at 2 Kmph, a motor boat goes 10 Km upstream and back again to the starting point in 55 minutes. Find the speed of motor boat in still water? 

   A.) 18 kmph
   B.) 22 kmph
   C.) 16 kmph
   D.) 20 kmph

Answer: Option 'B'

Let the speed of motor boat instill water be X kmph 
Then, speed in downstream = (X + 2) km 
and. speed in upstream = (X - 2) kmph 
Time taken to row 10km & back = (10/X+2,10/X-2) 
10/X+2 + 10/X-2 = 55/60 
11X2 - 240X - 44 = 0 
(X - 22)(11x + 2) = 0 
X = 22 or X = -2/11 
Then X = 22 kmph

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4.

A man rows to a place 48 Km distance and back in 14 hours. He finds that he can row 4 Km with the stream in the same time 3 Km against the stream. The rate off the stream is? 

   A.) 1 kmph
   B.) 2 kmph
   C.) 1.5 kmph
   D.) None

Answer: Option 'A'

Let be moves 4km downstream in X Hours 
Then in speed downstream = Kmph 
Speed in upstream = 4/X Kmph 
==> 48/4/X + 48/3/X = 14 
==> 12X + 16X =14 
==> X = 1/2 
Speed in downstream = 8 Kmph 
Speed in up stream = 6 Kmph 
Then the Rate of stream = 1/2 (8 - 6) = 1 Kmph

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5.

A man can row 8 Kmph in still water. If the velocity of the current is 2 Kmph and it takes him 2 hours to row to a place and come back. How far is the place? 

   A.) 6.5 km
   B.) 7.5 km
   C.) 7.4 km
   D.) 6.4 km

Answer: Option 'B'

Man's rate down stream = 8 + 2 = 10 kmph 
Man's rate upstream = 8 - 2 = 6 kmph 
Let the required distance be X km 
Then X/10 + X/6 = 2 
3X + 5X = 60 
8X = 60 
X = 7.5 km

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6.

A boat can travel 8 Km an hour in still water, but it takes thrice as much time for travelling the same distance against the current. The speed of the current (in Kmph) is: 

   A.) 29
   B.) 21
   C.) 41
   D.) 30

Answer: Option 'C'

41

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7.

In an hour a boat goes 10 Km along the stream and 4 Km against the stream. The speed of the boat in still water (in Kmph) is: 

   A.) 7 Kmph
   B.) 8 Kmph
   C.) 6 Kmph
   D.) 10 Kmph

Answer: Option 'A'

Let the speed of stream = X Kmph 
and the speed of water = 8 Kmph 
X + Y = 10 
X - Y = 4 
X = 7, Y = 3 
Speed of stream = 7 Kmph

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8.

A boat man goes 4 Km against the current of the stream in 1hour and goes 2 Km along the current in 5 minutes. How long will it take to go 21 Km in stationary water? 

   A.) 1 Hour
   B.) 1 Hour 15 Minutes
   C.) 1 Hour 30 Minutes
   D.) 1 Horr 45 Minutes

Answer: Option 'B'

1 Hour 15 Minutes

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9.

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.) 2 km/hr
   B.) 1 km/hr
   C.) 1.5 km/hr
   D.) 2.5 km/hr

Answer: Option 'B'

Suppose he move 4 km downstream in x hours.
Then, Speed downstream = ( 4/ x ) km/hr.
Speed upstream = (3/ x ) km/hr.
Therefore, 48 / ( 4 / x ) + 48 / (3/x) = 14 or x = 1/2 .
So, Speed downstream = 8 km/hr,
Speed upstream = 6 km/hr.
Rate of the stream = 1 / 2 (8-6) km/hr = 1 km/hr

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10.

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.) 2:01
   B.) 3:01
   C.) 3:05
   D.) 3:02

Answer: Option 'B'

Let man's rate upstream be x kmph.
Then, his rate downstream = 2x kmph.
Therefore , (Speed in still water) : (Speed of stream) = ( 2x + x /2) : ( 2x - x /2) = 3x / 2 : x /2 = 3: 1

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