Question

A motorboat covers a given distance in $6$ hours moving downstream on a river. It covers the same distance in $10$ hours moving upstream. The time it takes to cover the same distance in still water is:

• A. $6.5$ hours
• B. $8$ hours
• C. $9$ hours
• D. $7.5$ hours

Answer 1

Answer: (D)

$7.5$ hours

Let velocity in still water be $S$

Velocity of water be $W$

distance to be covered be $D$

$D=6(S+W)$

$D=10(S-W)$

which gives $S=4W$

So, $D=7.5hrs$.