Ratio of the speed of the stream and downstream speed of the boat is 3:10 respectively. If the boat covers 280 km in still water in 8 hours, then find the time taken by the boat to cover 300 km upstream?
A. 9 hours
B. 11 hours
C. 7 hours
D. 15 hours
E. None of these
Sol:
Let the speed of the stream=x km/hr
Speed of the boat in still water=280/8=35 km/hr
Downstream speed of the boat=(x+35) km
(x+35)/x=10/3
3x+105=10x
x=105/7
x=15 km/hr
Upstream speed of the boat=35-15=20 km/hr
Required time=300/20=15 hours
