How can they all cross the river in the boat?

Question

Two boys weighing 50 kgs each and their older brother weighing 100 kgs wish to cross the river. Their boat will only hold 100 kgs.
How can they all cross the river in the boat?

Answer 1

1. Both 50 kg boys move from A to B
2. 1 stays at B and 1 returns to A
3. 100 kg boy goes from A to B
4. 50 kg boy moves from B to A
5. Both 50 kg boys come to B.

All have now crossed over from A to B.