The boat, moving along the river, in 7 hours covers the same distance that it covered in 8 hours against the current.

The boat, moving along the river, in 7 hours covers the same distance that it covered in 8 hours against the current. What is the speed of the river flow if the boat’s own speed is 30 km / h?

1. Let’s say the speed of the river is x km per hour.
2. Then the speed of the boat along the river is (30 + x) km per hour.
3. The speed of the boat against the flow of the river is equal to (30 – x) km per hour.
4. The distance that the boat traveled along the river in 7 hours is 7 * (30 + x) km.
5. The distance that the boat traveled against the river flow in 8 hours is 8 * (30 – x) km.
6. Let’s make an equation and find out the speed of the river, if in both cases the path is the same.
7 * (30 + x) = 8 * (30 – x);
210 + 7x = 240 – 8x;
7x + 8x = 240 – 210;
15x = 30;
x = 30/15;
x = 2 km per hour.
Answer: The speed of the current is 2 km per hour.