Ken's blog

Fred and Mary were trying to work out how to give five gifts to their three boys for Christmas.

The kids, Henry, Mark and Joe, had told them they wanted to receive gifts more or less at random this year to see how the gifts would be distributed.

“We have five gifts to give to three children. How are we going to do this, Mary? There are so many possibilities it makes my brain spin,” said Fred in exasperation.

“Well, Fred, we have to make sure they all get at least one gift, so that makes it easier than the way you are thinking of, doesn’t it,” Mary said reassuringly.

“You’re right, Mary. The number of ways of giving the gifts so that our kids might not receive even one gift is quite large,” said Fred.

“Do it my way and the matter becomes more simple,” said Mary.

So Mary and Fred distributed the gifts as she suggested.

If they distributed the gifts Fred’s way what would be the probability that one or more of the kids received no gift?