How long does it take for a boat to swim 90 km up the river if the speed of the boat

How long does it take for a boat to swim 90 km up the river if the speed of the boat is 20 km / h and the speed of the river is 2 km / h?

The expression “upriver” is against the stream. We find the speed of movement against the flow of the river:
20 – 2 = 18 (km / h).
We find the time for which the boat will sail 90 km:
90/18 = 5 (hours).
Answer: the boat needs 5 hours.



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