Question

12. A man whose speed is 4.5 kmph in still water rows
to a certain upstream point and back to the starting
point in a river which flows at 1.5 kmph, find his
average speed for the total journey ?
(A) 8 kmph
(B) 4 kmph
(C) 2 kmph
(D) 10 kmph​

Answer 1

Answer:

4Km/h

Step-by-step explanation:

Speed of man = 4.5Km/h

Speed of stream = 1.5Km/h

Speed of downstream = 4.5 + 1.5 = 6Km/h

speed of upstream = 4.5 - 1.5  = 3Km/h

total time = 9

Average Speed = (2 x 6 x 3)/9 = 4 km/h.