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erica [24]
3 years ago
13

Bob can row 14 mph in still water. The total time to travel downstream and return upstream to the starting point is 4 hours. If

the total distance downstream and back is 42 miles, determine the speed of the river (current speed).
Physics
1 answer:
bija089 [108]3 years ago
7 0

Answer:

7 mph

Explanation:

Let the speed of river is c mph.

The effective downstream speed = 14 + c

The effective upstream speed = 14 - c

Total time = 4 hrs

Total distance = 42 miles

Time for upstream + time for downstream = 4 hrs

21 / (14 + c) + 21 / (14 - c) = 4

21 (14 - c + 14 + c) = 4 (196 - c^2)

21 x 28 = 4 (196 - c^2)

c^2 = 196 -147 = 49

c = 7 mph

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