The boat went downstream for 5 hours, and the same way upstream in 6 hours. How long will the raft travel?

Suppose the specified distance is 1.

In this case, the conditional speed of the boat downstream will be:

1/5 = 1/5 part of the way per hour.

The upstream speed will be:

1/6 = 1/6 part of the way per hour.

Speed difference:

1/5 – 1/6 = 6/30 – 5/3 = 1/30.

From this it follows that the speed of the river will be equal to:

1/30/2 = 1/30 * 1/2 = 1/60 part of the way per hour.

The speed of the current is the speed of the raft, so it will travel the specified distance in:

1 / 1/60 = 1 * 60/1 = 60 hours.