Four brothers, John, Jack, Jeff, and Jim are standing on one side of a river. They need to cross the river in 18 or less hours. They have a boat that carries only two people at a time.
The time it takes to cross the river is the time it takes the slowest person to cross it, so if Jack and Jim are in the boat, it'll take them 10 hours.
- John can row the boat to the other side in 1 hour.
- Jack can row to the other side in 2 hours.
- Jeff can row to the other side in 5 hours.
- Jim can row to the other side in 10 hours.
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