Richard Hovasse's bridge and torch problem (also known as The Midnight Train and Dangerous crossing) is a logic puzzle that deals with four people, a bridge and a torch.
Ahmed, Bindi, Cassandra and Donavan have to cross a dangerous bridge in the mountains late one night. They have only one weak torch to share and because of the weak light and nature of the bridge, only two of them can cross at any time. Now, they must cross with the torch and, when two people cross, they must travel at the pace of the slower person.
They have discovered that the bridge has been rigged with explosives and will be deomolished in exactly 18 minutes. It is vital that they cross within that time frame!
Finally, Ahmed can cross the bridge in one minute; Bindi can cross in two minutes; Cassandra will take five minutes; and Donovan (who is injured) will take ten minutes.
Your challenge is to work out a strategy to get all four people across the bridge in less than 18 minutes. There is no trick to this. You don't have to think of flying, climbing, swimming, crossing three at a time, or anything like that. Treat this as the 'standard' puzzle that it is.
I really can be done!
Answer: 