Rajat can row at 9 km/h in still water. He rows to a jetty 24 km upstream and comes straight back, the whole trip taking 6 hours. The speed of the stream (in km/h) is:

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3. 24/(9 − s) + 24/(9 + s) = 6 → 24(9 + s) + 24(9 − s) = 6(81 − s²) → 432 = 486 − 6s² → 6s² = 54 → s = 3 km/h. (Check: 24/6 = 4 h upstream and 24/12 = 2 h back.) Working from the round-trip average 48/6 = 8 km/h and taking 9 − 8 = 1 is not the stream speed — the two legs take unequal times.

Rajat can row at 9 km/h in still water. He rows to a jetty 24 km upstream and comes straight back, the whole trip taking 6 hours. The speed of the stream (in km/h) is:

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