# It took a crew 2 h 6 min to row 7 km upstream and back again. If the rate of flow of the stream was 8 km/h, what was the rowing speed of....?

It took a crew 2 h 6 min to row 7 km upstream and back again. If the rate of flow of the stream was 8 km/h, what was the rowing speed of the crew in still water?

### 1 Answer

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- MichaelLv 71 month ago
time = distance/ speed

Time against current + time with current = 2hr 6 min = 2.1hr

7/(s - 8) + 7/(s + 8) = 2.1

Multiply both sides by (s - 8)(s + 8)

7(s + 8) + 7(s - 8) = 2.1(s - 8)(s + 8)

14s = 2.1(s² - 64)

14s = 2.1s² - 134.4

2.1s² - 14s -134.4 = 0

Solve using quadratic equation (work not shown)

s = {-5.333, 12}

The speed is positive

12 k/hr <–––––

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