exam Maths Puzzle

Rahul can row a certain distance downstream in 6 hour and return the same distance in 9 hour. If the speed of Rahul in still water is 12 km/hr, Find the speed of the stream.

A.

2 km/hr

B.

2.4 km/hr

C.

3 km/hr

D.

1.5 km/hr

Read Solution (Total 1)

Assume speed of stream = x
downstream=12+x
upstream=12-x
distance of stream:
downstream dis=12*6=72km
upstream dis=12*9=108km
total time taken=9+6=15
w.k.t,speed=dis/time
so,time=dis/speed
now,
[72/(12+x)]+[108/(12-x)]=15
By solving the above eqn,
15x^2+36x=0
we get x=2.4km/hr
8 years agoHelpfull: Yes(1) No(1)

exam Other Question

A car driver driving in fog, passes a pedestrian who was walking at the rate of 2km/h in the same direction. The pedestrian could see the car for 6 min and it was visible to him up to a distance of 0.6 km. The speed of the car would be :

A.

8 km/h

B.

800 m/h

C.

200 m/h

D.

15 km/h
In a race, the speeds of A and B are in the ratio 3:4. A takes 30 minutes more than B to reach the destination. The time taken by A to reach the destination is:

A.

1 hr

B.

1.5 hr

C.

2 hr

D.

2.5 hr