The boat sailed along the river for 5 hours, and against the river for 3 hours. The boat’s own speed is 18 km / h.

| June 23, 2021 | education

The boat sailed along the river for 5 hours, and against the river for 3 hours. The boat’s own speed is 18 km / h. Find the speed of the river flow if the boat sailed 48 km more downstream than upstream.

The speed of the river flow is taken as X (km / h),

then the speed of the boat along the river will be V1 = (18 + x) km / h,

and the speed of the boat against the river is V2 = (18 – x) km / h.

The distance traveled by the boat is found by the formula: S = V * t,

where S is distance (km), V is speed (km / h), t is time (h).

In 5 hours the boat will pass along the river S1 = (18 + x) * 5 (km);

For 3 hours upstream – S2 = (18 – x) * 3 (km).

We make the equation: S1 – S2 = 48.

(18 + x) * 5 – (18 – x) * 3 – 48,

90 + 5x – 54 + 3x = 48,

8x = 48 – 90 + 54,

8x = 12,

x = 1.5 (km / h) – the speed of the river.



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