Question

If speed of boat in upstream is double than the speed of current and speed of boat in still water is 27 km/hr.then find the time taken by boat to travel 54 km downstream..?

Answer 1

given, speed of boat in still water , $v_b$ = 27 km/h

speed of boat in upstream is double than speed of current.

Let speed of current is x

then, speed of boat in upstream, $v_b-x$ = 2x

or, $v_b=3x$

or, 27 = 3x

or, x = 9

hence, speed of current is 9km/h.

now, speed of boat in downstream = $v_b+x$

= 27 + 9 = 36 km/h

so, time taken by boat to travel 54km downstream = 54km/(36km/h)

= 1.5 hr