Question

A streamer goes downstream from one port to another in 4 hours.It covers the same distance upstream in 5 hours.If the speed of stream is 2 km/h, the distance between the two ports is

• A. $80$ km
• B. $81$ km
• C. $70$ km
• D. $71$ km

Answer 1

The correct option is A $80$ km

Let speed of the streamer in still water= x km/hr
Speed of downstream =(x+2)km/hr
Distance between the ports $=4(x+2)$km.... (i)
Speed of upstream =(x-2)km/hr
Distance between the ports $=5(x-2)$km....(ii)
from Equation (i) and (ii)
$4(x+2)=5(x-2)$
$4x+8=5x-10$
$x=18$
$\therefore$ Distance between two ports $=4(x+2)$
$=4(18+2)km=80km$