A bridge is about to collapse! 4 people need to cross it and get to the other side before it will collapse. It is a dark night and hard to see to the other side- there is only one torch between them.
Only two people can cross at a time and the torch is used to light their way.
Al takes a minute to cross.
Bob takes 2 minutes.
Chris takes 5 minutes.
Dan takes 10 minutes.
Solve- how do all people make it across to the other side? What is the quickest amount of time for all 4 people to cross before the bridge collapses? Type out your answer and explain your solution.