Question

A sailor goes 8 km downstream in 40 minutes and returns in 1 hour. Find the speed of the sailor in still water and the speed of the current.

Answer 1

Let the speed of the sailor in still water be x km/h and that of the current y km/h.

Speed downstream = (x + y) km/h

Speed upstream = (x – y) km/h

As per the question

`(x + y) xx 40/60 = 8`

⇒ x + y = 12   ...(i)

When the sailor goes upstream, then

(x – y) × 1 = 8

x – y = 8   ...(ii)

Adding (i) and (ii), we get

2x = 20

⇒ x = 10

Putting x = 10 in (i), we have

10 + y = 12

⇒ y = 2

Hence, the speeds of the sailor in still water and the current are 10 km/h and 2 km/h respectively.