Question

A motorboat goes downstream at covers a distance in 4 hours while it covers the same distance upstream in 5 hours if the speed of the stream is 3 km per hour find the speed of the motor boat in still water

Answer 1

let the speed of the motorboat be X.
speed of motorboat in downstream=x+3
speed of motorboat in downstream=x-3
since,distance=time x speed
therefore,
distance travelled by speed of X+3=4(X+3)
distance travelled by speed of x+-3=5(x-3)
since distance travelled was same, so
4(X+3)=5(x-3)
4x+12=5x-15
4x-5x=-15-12
-x=-27
X=27

therefore, the speed of motorboat is 27 km/hr

Answer 2

answer:

let the speed of the motorboat be x

speed of motorboat in downstream=x+3

speed of motorboat in downstream=x-3

since,

distance=time x speed

distance travelled by speed of x+3=4(x+3)

distance travelled by speed of x+3=5(x-3)

=4(x+3)=5(x-3)

=4x+12=5x-15

=4x-5x=-15-12

=-x=-27

=x=27

=27 km/hr