A motorboat in still water travels at a speed of 36 kmph It goes 56 km upstream in 1 hour 45 minutes...........

Explanation:

?Speed of motar boat in still water, x = 36 km/h
Speed of upstream, U
= 56 km/(1 + 3/4) = 56 × 4/7 = 32 km/hr
According to the question,
x – y = U
36 – y = 32
y = 4 km/h
Speed of Downstream, D
= x + y
= 36 + 4
= 40 km/h
Time taken to cover the distance downstream
= 56/40 h
1 hours 24 minute