Distances between piers A and B the raft sails in 15 minutes, and the boat sails the distance AB against the river

Distances between piers A and B the raft sails in 15 minutes, and the boat sails the distance AB against the river flow in 30 minutes. in how many minutes will the boat sail the distance AB downstream?

We take the distance between the piers equal to 1.

We find the conditional speed of the river.

Divide the distance between A and B by the time the raft is moving.

1/15 = 1/15 part of the way per hour.

We find the speed of the boat against the stream of the river.

1/30 = 1/30 part of the way per hour.

Let’s find the boat’s own speed.

To do this, we add the current speed to its speed upstream.

1/30 + 1/15 = 1/30 +/30 = 3/30 = 1/10 part of the way per hour.

Find the speed with the flow.

1/10 + 1/15 = 3/30 + 2/30 = 5/30 = 1/6.

The boat travel time will be:

1 / 1/6 = 1 * 6/1 = 6 hours.

Answer:

6 o’clock.



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