The boat passed downstream in 5 hours, and against the current in 6 hours. How long will the raft sail only downstream?

Suppose that the boat’s own speed is equal to x km / h, and the current speed is equal to y km / h, then the boat will go downstream at a speed x + y km / h, and against the current at a speed x – y km / h.

We get the following equation:

5 * (x + y) = 6 * (x – y),

5 * x + 5 * y = 6 * x – 6 * y,

x = 11 * y.

Then the distance traveled can be written as follows:

5 * (x + y) = 5 * (11 * y + y) = 5 * 12 * y = 60 * y.

Since the raft moves at the speed of the river, it will cover this distance in:

60 * y: y = 60 hours.