A boat covers x km downstream in 6 hours and also covers the same distance upstream in 15 hours. If the speed of the stream is decreased by 20%, then the time taken by the boat to cover 235 km downstream is 5 hours. Find the value of x?
A. 210
B. 300
C. 160
D. 100
E. None of these
Sol:
Speed of the boat=y
Speed of the stream=z
x/(y+z)=6
x/(y-z)=15
6y+6z=15y-15z
9y=21z
y=7z/3
235/(7z/3+z*4/5)=5
705=47z
z=15
Speed of the stream=15 kmph
Speed of the boat=35 kmph
x/(y+z)=6
x/(35+15)=6
x=300 km
