A family of four members (Father, Mother, Daughter and Son) set up a camp near the bank of a river. At midnight they discovered that the forest behind them has caught fire and is rapidly approaching them. The only choice the family has got is to cross the river (they have a boat which can carry a maximum of two members). All the family members know how to row the boat but with different speeds (Father, Mother, Daughter and Son can row to other side of the bank in 1min, 2min, 5mins and 10mins respectively). The pairs must row at the speed of the slowest person. Also the boat cannot cross the river without a person on it. Given the limitations what is the shortest possible time in which the entire family can safely cross the river?
Daughter and Son go first (2mins). Daughter comes back (1min). Then Father and Mother cross (10mins). Son comes back (2mins) and then crosses with daughter (2mins).
Total: 17 mins