The boat went with the stream for 1 hour, and back against the stream for 84 minutes.

| January 13, 2021 | education

The boat went with the stream for 1 hour, and back against the stream for 84 minutes. Find your own speed of the boat, if you know that the speed of the river is 2 km / h, but only 28 km passed?

Let the boat’s own speed be x km / h, then the speed of the boat along the river is (x + 2) km / h, and the speed of the boat against the river is (x – 2) km / h. In 1 hour along the river the boat covered 1 (x + 2) km, and in 84 minutes = 1.4 hours against the river, it covered 1.4 (x – 2) km. It is known that in total the boat covered a distance equal to ((x + 2) + 1.4 (x – 2)) kilometers or 28 km. Let’s make an equation and solve it.
(x + 2) + 1.4 (x – 2) = 28;
x + 2 + 1.4x – 2.8 = 28;
2.4x – 0.8 = 28;
2.4x = 28 + 0.8;
2.4x = 28.8;
x = 28.8: 2.4;
x = 12 (km / h).
Answer. 12 km / h



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