The greatest math blog ever.
Four people want to cross a slippery bridge on a dark moonless night. There is only one flashlight. The bridge is very dangerous so every time somebody crosses the bridge, someone has to bring the flashlight. The bridge is very weak so only two people can cross it at a time. And they have to walk at the speed of the slowest person. The fastest person can cross in 1 minute. The second fastest can cross in 2 minutes, the third fastest can cross in 5 minutes, and the slowest can cross in 10 minutes. Can you get everyone across in 17 minutes? Let me know the order that the people crossed.
Hint: There are no tricks. And no you can’t throw the flashlight or find a helicopter or any weird ideas. Just try some different groups.