A motorboat moves downstream at 56 km/h. After

Solution

ATQ,

Let the speed of the stream be ‘x’ km/h. Original time for the whole journey = 560/56 = 10 hours So, time taken to cover the first half = 10 ÷ 2 = 5 hours New total time (because of early arrival) = 10 hours − 20 minutes = 9 hours 40 minutes = 9.666… hours So, time taken for the second half now = 9.666… − 5 = 4.666… hours (i.e., 4 hours 40 minutes) So, speed in the second half = 280 / 4.666… = 60 km/h Net change in speed = 60 − 56 = 4 km/h Increase due to stream = 1.25x − x = 0.25x So, 0.25x = 4 ⇒ x = 16 Therefore, the original speed of the stream = 16 km/h