A farmer is looking to hire some hired hands. His usual three hires are named Barry, Harry, and Larry.
He knows from hiring them before that:
- Working together, Barry and Harry can plow an acre in two hours.
- Working together, Barry and Larry can plow an acre in three hours.
- Working together, Harry and Larry can plow an acre in five hours.
How many hours would it take for all three of them working together to plow an acre?