Brainteaser #15 – Over the Bridge

Zombie brainteaser

Red alert! Zombies have been released from a scientific testing facility and are swarming the building. The staff of the facility muster near the entrance and begin to hatch their escape plan. There is one remaining obstacle – a drawbridge that leads out of the facility.

There are 4 individuals present:

  • A student
  • A lab technician
  • The security guard
  • The professor

The student is young and can easily cross the bridge in one minute. The lab assistant, also young, can cross it in two minutes. The security guard can cross it in five minutes. The older professor has a walking stick and needs 10 minutes.

It’s dark, dangerous and the group carries one torch that has to be carried on any trip across the bridge.

The zombies are predicted to arrive in just 17 minutes and the bridge’s maximum capacity is two people at any one time.

How can you get everyone across in 17 minutes before the zombies arrive, allowing you to raise the drawbridge and lock them in?

First, the student and lab assistant cross together and the student returns with the torch. This takes 3 minutes.

The professor and security guard takes the torch and cross, taking 10 minutes in total. The clock is at 13 minutes.

The lab assistant takes the torch and crosses, taking another 2 minutes. The student and lab assistant then cross back over. This takes them right up to the 17-minute mark!

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