The downstream speed of a boat is 8 km/hr more than its
upstream speed and the ratio of the speed of the boat in still water to the speed of the stream is 5:2. Find the total time taken by boat to travel 42 km downstream and 36 km upstream?
A12 hrsCorrect AnswerIncorrect Answer
B10 hrsCorrect AnswerIncorrect Answer
C16 hrsCorrect AnswerIncorrect Answer
D9 hrsCorrect AnswerIncorrect Answer
E7 hrsCorrect AnswerIncorrect Answer
Solution
Let the speed of boat in still water be x km/hr and that of stream be y km/hr. ATQ, ⇒ (x + y) – (x – y) = 8 ⇒ y = 4 km/hr ⇒ x = 4 × 5/2 = 10 km/hr Required time = [42/(10+4)] + [36/(10−4)] = 9 hr