Mr. smith has two children. if the older child is a boy, what are the odds that the other child is also a boy?

50% Because 2 people are there and if 1 is a boy there's a 50% chance that there's another boy.   For example you had 2 gumballs in a gumball machine. You picked one up. There would be chances of picking up 1 of the other. So there's a 50% chance of picking a gumball. :D hope this helps.