Aptitude

A boat travels upstream from B to A and downstream from A to B in 3 hours. If the speed of the boat in still water is 9km/hr and the speed of the current is 3km/hr, the distance A and B is:_______?

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A boat travels upstream from B to A and downstream from A to B in 3 hours. If the speed of the boat in still water is 9km/hr and the speed of the current is 3km/hr, the distance A and B is:_______?

A. 4km
B. 6 km
C. 8 km
D. 12 km
Explanation:
Speed downstream = (9+3) km/hr = 12km/hr
Speed upstream = (9-3) km/hr = 6 km/hr
Distance AB = x km
x/6 + x/12 = 3
=> 2x + x = 36
=> x= 12

A boat takes half time in moving a certain distance downstream than upstream. What is the ratio between the rate in still water and rate of current?

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A boat takes half time in moving a certain distance downstream than upstream. What is the ratio between the rate in still water and rate of current?

A. 1 : 2
B. 3 : 1
C. 2 : 1
D. 1 : 3
Explanation:
Let the speed of the boat in still water be 4 km/hr and speed of the current be u km/hr.
Rate downstream = (u + v) km/hr.
Rate upstream = (u- v)km/hr
Let the distance covered in each case be x km.
Then 2x/(u + v) = x / (u – v)
=> 2 (u – v) = ( u + v)
=> u =3v
=> u/v =3/1

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 he take to go 5km in stationery water?

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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 he take to go 5km in stationery water?

A. 40 Minutes
B. 1 Hour
C. 1 hr 15 Min
D. 1 Hr 30 Min
Explanation:
Speed upstream = 2km/hr.
Speed downstream = 6 km/hr
Speed in stationary water = ½ (6 + 2) km/hr = 4 km/hr
Time is taken to cover 5 km in stationary water
= (1/4 x 5) 1 hr 15 min

A man can row 7 ½ kms on hour in still water and he finds that it takes hi twice as long to row down the river. The rate of stream is

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A man can row 7 ½ kms on hour in still water and he finds that it takes hi twice as long to row down the river. The rate of stream is

A. 2.4km/hr
B. 2.5 km/hr
C. 3.4km/hr
D. 3.5km/hr
Explanation:
Let the rate of the stream be x km/hr.
Then Speed downstream = (15/2 + x)km/hr.
Speed upstream = (15/2 -x)km/hr
(15/2 + x) = 2 (15/2 – x)
=> 3x =15/2
=> x = 15/6 = 5/2 = 2.5
Therefore, Rate of stream = 2.5 km/hr

A man can row three-quarters of a kilometer against the stream in 11 ¼ minutes and return in 7 ½ minutes. The speed of the man in still water is________?

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A man can row three-quarters of a kilometer against the stream in 11 ¼ minutes and return in 7 ½ minutes. The speed of the man in still water is________?

A. 2km/hr
B. 3km/hr
C. 4 km/hr
D. 5 km/hr
Explanation:
Distance covered upstream in 45/4min =3/4 km
Distance covered upstream in 1 hr =(3/4 × 2/15 × 60) km/hr = 4 km/hr
Distance covered downstream in 15/2 min = ¾ km
Distance covered downstream in 1hr
= (3/4 × 2/15 × 60)km/hr = 6 km/hr
Speed of the man in still water
= ½ (6 + 4)km/hr = 5 km/hr

A boat goes 6 km in an hour in still water. It takes thrice as much time in covering the same distance against the current. Speed of the current is_______?

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A boat goes 6 km in an hour in still water. It takes thrice as much time in covering the same distance against the current. Speed of the current is_______?

A. 2 km/hr
B. 3km/hr
C. 4km/hr
D. 5 km/hr
Explanation:
Speed in still water = 6 km/hr
Speed against the current = 6/3 km/hr = 2 km/hr
Let the speed of the current be x km/hr
6-x = 2 => x =4 km/hr

A boat running upstream takes 8 hours 48 min 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 the speed of water current respectively?

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A boat running upstream takes 8 hours 48 min 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 the speed of water current respectively?

A. 2 : 1
B. 3 : 1
C. 8 : 3
D. Cannot be determined
Explanation:
Let the speed of boat be x km/hr and speed of stream be ykm/hr.
44/5 × (x -y) = 4x (x +y)
=> 44(x-y) = 20 (x+y)
=>11 (x-y) = 5 (x +y)
=> 6x =16 y
=> x/y = 16/6 = 8/3
=> x : y = 8 : 3

A man can row at 5 km/hr in still water, if the river is running at 1 km/hr it takes him 75 minutes to row to a place and back. How far is the place?

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A man can row at 5 km/hr in still water, if the river is running at 1 km/hr it takes him 75 minutes to row to a place and back. How far is the place?

A. 2.5km
B. 3km
C. 4 km
D. 5 km
Explanation:
Speed downstream = (5+1)km/hr = 6 km/hr
Speed upstream = (5-1)km/hr = 4 km/hr
Let the required distance be x km.
Then x/6 + x/4 = 75/60 = 5/4 => (2x + 3x) =15 => x =3.
Required distance = 3 km