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?
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
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?
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
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?
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
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?
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
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?
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
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:
Answer: Option 'C'
41
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:
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
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?
Answer: Option 'B'
1 Hour 15 Minutes
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:
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
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:
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