Question

A sailor goes 8 km downstream in 40 minutes
and comes back in one hour. Determine the
speed of the current.
(A) 10 km/hr
(B) 2 km/hr
(D) 8 km/hr
(C) 12 km/hr​

Answer 1

Step-by-step explanation:

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

Then, speed of sailor downstream =x+y km/hr and speed of sailor upstream =x−y km/hr.

Distance covered =8 km.

Also, Time=SpeedDistance

From the given information, we have,

x+y8=6040andx−y8=1or,x+y8=6040=>x+y8=32=>24=2(x+y)=>x+y=12....(i)Also,x−y8=1=>x=8+y....(ii)

Substituting (ii) in (i), we get,

x+y=12=>8+y+y=12=>2y=4=>y=2

Substituting y=2 in equation (ii), we get,

x=8+y=>x=8+2=>x=10

Therefore, speed of sailor in still water 

=x=10km/hr and speed of the cureent =y=2km/hr

Answer 2

Step-by-step explanation:

x= 10 km

y= 2km

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