Cross the Bridge

Puzzle • Mathematics

Max Score: 40


Four people are on this side of the bridge. Everyone has to get across.

Problem is that it’s dark and so you can’t cross the bridge without a flashlight and they only have one flashlight.

Plus the bridge is only big enough for two people to cross at once.

The four people walk at different speeds:

  • one fella is so fast it only takes him 1 minute to cross the bridge,

  • another 2 minutes,

  • a third 5 minutes,

  • the last it takes 10 minutes to cross the bridge.

When two people cross the bridge together (sharing the flashlight), they both walk at the slower person’s pace. What is the minimum time required for all 4 to cross the bridge.

Respond with a number which represents the number of minutes.

Answer is a integer. Just put the number without any decimal places if its an integer. If the answer is Infinity, output Infinity.

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