A family is fleeing their oppressive country late one night. They come to the country's border, a gaping chasm, the only crossing being a rickety bridge. The bridge is only strong enough to support two people at a time (as stated by the conveniently placed sign). As it is dark, a torch is needed to cross the bridge to make sure no one steps on rotten planks. The family only have one torch between them, hence only up to two of them can cross at a time.
The fit and healthy father can cross the bridge in 1 minute.
The aged but healthy grandmother can cross the bridge in 2 minutes.
The pregnant mother can cross the bridge in 5 minutes.
The hobbling, arthritic grandfather can cross the bridge in 10 minutes.
The secret police are only 17 minutes behind them. How can they cross the bridge safely and flee their country before the secret police arrive?
