Time and Distance Q.5

5A man rows a boat at the speed of 12 km per hour in still water to some upstream point and back to the starting point. The speed of flow of river is 3 km per hour. Find his average speed (in kms) per hour for the total journey.

Option : A
Explanation : Speed of the man in still water = 12 km/hr
Speed of the stream = 3 km/hr
Speed downstream = (12 + 3) = 15 km/hr
Speed upstream = (12 – 3) = 9 km/hr
Let the distance travelled be ‘d’ km Then
$TIME AND DISTANCE$

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