Question

A man can row at a speed of $5km/h$ in still water. How long will he take to travel $10km$ up the stream and back to the starting point when the speed of the river is $3km/h$?

• A. 6 hours 15 minutes
• B. 6 hours
• C. 5 hours 45 minutes
• D. 6 hours 25 minutes

Answer 1

The correct option is A 6 hours 15 minutes

Time taken to travel upstream = $T_1=\frac{10}{(5-3)}=5h$,
Time taken to travel downstream back to the starting point = $T_2=\frac{10}{(5+3)}=1.25h$
Total time = $T=5+1.25=6.25h$
Hence the correct option is (a).