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
11.
Speed of a boat in standing water is 9 kmph and the speed of the stream is 1.5 kmph. A man rows to a place at a distance of 105 km and comes back to the starting point. The total time taken by him is:
Answer: Option 'D'
Given
Distance = 105 km
Speed upstream = 7.5 kmph.
Speed downstream = 10.5 kmph.
Total time taken = Distance / Speed inupstream + Speed indownstream
= ( 105 / 7.5) + (105 / 10.5 ) hours
= 14 + 10
= 24 hours.
Total time taken by him = 24 hours.
12.
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?
Answer: Option 'C'
Rate downstream = ( 1 / 10 x 60 ) km/hr = 6 km/hr
Rate upstream = 2 km/hr.
Speed in still water = 1/2 (6 + 2) km/hr = 4 km/hr.
Therefore, Required time = ( 5/4 ) hrs = 1 ( 1/4 ) hrs = 1 hr 15 min.
13.
A boat covers a certain distance downstream in 1 hour, while it comes back in 1 1/2 hours. If the speed of the stream be 3 kmph, what is the speed of the boat in still water?
Answer: Option 'D'
Let the speed of the boat in still water be x kmph.
Given,speed of the stream = 3 kmph
Then, Speed downstream = speed of the boat +speed of the stream
= (x + 3) kmph
Speed upstream = speed of the boat - speed of the stream
= (x - 3) kmph.
Therefore, Downstream distance =upstream distance
=> SpeedDownstream * Downstream Time =Speedupstream *upstream Time
=> (x + 3) x 1 = (x - 3) x 3/2
=> 2x + 6 = 3x - 9
=> x = 15 kmph.
Thus,speed of the boat in still water = 15 kmph
14.
A man can row at 5 kmph in still water. If the velocity of current is 1 kmph and it takes him 1 hour to row to a place and come back, how far is the place?
Answer: Option 'A'
If the speed of a boat in still water is xkm/hr and the speed of the stream is ykm/hr, then:
Speed downstream = (x+ y) km/hr.
Speed upstream = (x- y) km/hr.
Speed downstream = (5 + 1) kmph = 6 kmph.
Speed upstream = (5 - 1) kmph = 4 kmph.
Let the required distance be x km.
Distance / Speed = Time
Given, Time fordownstream+ upstream = 1 hour
Then, x / 6 + x / 4 = 1
=> 2x + 3x = 12
=> 5x = 12
=> x = 2.4 km
Thus, the required distance =2.4 km
15.
A boat takes 90 minutes less to travel 36 miles downstream than to travel the same distance upstream. If the speed of the boat in still water is 10 mph, the speed of the stream is:
Answer: Option 'A'
Let the speed of the stream be x mph.
Given, Speed of Boat = 10 mph
Then, Speed downstream = speed of Boat +Speed of Stream
= (10 + x) mph,
Speed upstream = speed of Boat -Speed of Stream
= (10 - x) mph.
Therefore, Upstream Time - Downstream Time = 90 mins
Since, Time = Distance / Speed
So, [Upstream Distance / Upstream Speed] - [Downstream Distance / Downstream Speed] = 90 mins
=> [36 / ( 10 - x)] - [36 / (10 + x )] = 90 / 60
=> 36 (10 + x -10 + x) / (10^2 - x^2) = 3/2
=> 12 (2x / 100 - x^2) = 1/2
=> 24 (2x) = 100 - x^2
=> 48 x = 100 - x^2
=> x^2 + 48x - 100 = 0
=> (x+ 50)(x - 2) = 0
=> x = 2 mph
Therefore,speed of the stream= 2 mph.
16.
The speed of a boat in still water is 15 km/hr and the rate of current is 3 km/hr. The distance travelled downstream in 12 minutes is:
Answer: Option 'D'
Speed downstream = (15 + 3) kmph = 18 kmph. Distance travelled = ( 18 x 12 / 60 ) km = 3.6 km.
17.
A boat running downstream covers a distance of 16 km in 2 hours while for covering the same distance upstream, it takes 4 hours. What is the speed of the boat in still water?
Answer: Option 'B'
Rate downstream = (16 / 2 ) kmph = 8 kmph
Rate upstream = (16/4) kmph = 4 kmph
Speed in still water = 1/2 (8 + 4 ) kmph = 6 kmph.
18.
In one hour, a boat goes 11 km/hr along the stream and 5 km/hr against the stream. The speed of the boat in still water (in km/hr) is:
Answer: Option 'C'
Speed in still water = 1/2 ( 11 + 5) kmph = 8 kmph.
19.
A motorboat, whose speed in 15 km/hr in still water goes 30 km downstream and comes back in a total of 4 hours 30 minutes. The speed of the stream (in km/hr) is:
Answer: Option 'B'
Let the speed of the stream be x km/hr.
Then, Speed downstream = (15 + x) km/hr,
Speed upstream = (15 - x) km/hr.
Therefore 30 / 15 + x + 30 / (15 - x ) = 4 (1/2)
=> 900 / 225 - x2 = 9/2
=> 9x2 = 225
=> x^^2 = 25
=> x = 5 km/hr
Therefore, the speed of the stream = 5 km/hr
20.
A man's speed with the current is 15 km/hr and the speed of the current is 2.5 km/hr. The man's speed against the current is:
Answer: Option 'C'
Man's rate in still water = (15 - 2.5) km/hr = 12.5 km/hr.
Man's rate against the current = (12.5 - 2.5) km/hr = 10 km/hr.