A boat travels 10 km upstream and 5 km downstream in 3 hrs. If the speed of the boat in still water is 7 kmph, find the speed of the stream.
A
2 kmph
B
3 kmph
C
4 kmph
D
5 kmph
Correct Option - B
Explaination
Let the speed of the stream be x kmph.
Upstream speed = (7-x) kmph
Downstream speed = (7+x) kmph
Time taken to travel upstream = (10/(7-x)) hrs
Time taken to travel upstream = (5/(7+x)) hrs
(10/(7-x)) + (5/(7+x)) = 3
3x2+5x-42=0
Solving this equation, x=3