The boat sailed along the river for 3.5 hours, and against the current – 2.5 hours

| March 28, 2021 | education

The boat sailed along the river for 3.5 hours, and against the current – 2.5 hours. In total, the boat sailed 49.8 km. The river speed is 1.8 km / h. Find your own boat speed.

Let the boat’s own speed be x km / h, then the speed of the boat along the river is (x + 1.8) km / h, and the speed of the boat against the river is (x – 1.8) km / h. The boat passed along the river in 3.5 hours a distance equal to 3.5 (x + 1.8) km, and against the river in 2.5 hours – 2.5 (x – 1.8) km. According to the condition of the problem, it is known that in total the boat covered 3.5 (x + 1.8) + 2.5 (x – 1.8) kilometers or 49.8 km. Let’s make an equation and solve it.

3.5 (x + 1.8) + 2.5 (x – 1.8) = 49.8;

3.5x + 6.3 + 2.5x – 4.5 = 49.8;

6x + 1.8 = 49.8;

6x = 49.8 – 1.8;

6x = 48;

x = 48: 6;

x = 8 (km / h).

Answer. 8 km / h.



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