Question

A boat covers a certain distance downstream in 2 hrs. It covers the same distance in 2.5 hrs upstream. The speed of a boat in still water is 18km/hr. Find the speed of the water. Also find the speed of the boat

Answer 1

ratio of time of downstream and upstream = 2 : 2.5

=2:5/2 = 4:5

therefore ratio of speed of downstream and upstream =5:4

let Downstream speed =5x and upstream speed =4x

then speed of boat = 5x +4x /2 = 9x/2 =18(given)

therefore x =18*2/9 =4

so downstream speed = 5x = 5*4 =20 km/hr

and upstream speed =4x =4*4=16 km /hr

hence speed of water D-U /2 = 20-16/2 =2km /hr

and speed of boat = 20+16/2 = 18 km /hr