# Cross a Bridge in the Middle of the Night

Four people need to cross a bridge in 17 minutes in the middle of the night. The bridge can only hold two or less people at any time and they only have one flashlight so they must travel together (or alone). The flashlight can only travel with a person so every time it crosses the bridge it must be carried back. Tom can cross in 1 minute, John can cross in 2 minutes, Sally can cross in 5 minutes, and Connor can cross in 10 minutes. If two people cross together they go as fast as the slower person.

How can they cross the bridge in 17 minutes or less?

### 2 guesses to Cross a Bridge in the Middle of the Night

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• Crabman

Tom & John cross +2 min (2 min elapsed)
Tom returns +1 (3)
Sally & Connor cross +10 (13)
John returns +2 (15)
John & Tom cross +2 (17)

Once I realized Sally & Conner must travel together it all fell into place.

• Crabman, you are today’s winner!
First Tom and John will cross (2 minutes). Then Tom will bring the flashlight back (1 minute). Next Sally and Connor will cross (10 minutes). Then John will bring the flashlight back (2 minutes). Finally John and Tom will cross (2 minutes). 2 + 1 + 10 + 2 + 2 = 17 minutes.