Speed in down stream = 10 +8 = 18
Time taken to cover 90 km down stream = 90/18 = 5 hrs.
A man can row a boat at 10 kmph in still water and the speed of the stream is 8 kmph. What is then time taken to row a distance of 90 km down the stream ?
A. 8hrs
B. 5 hrs
C. 15 hrs
D. 15 hrs
E. 20 hrs