Probability questions, at the eleven plus level, often seem to involve cards. For some reason or another the writers of some eleven plus mathematics papers appear to take it for granted that all eleven plus children have access to packs of cards at school or at home. There will be some children, for one reason or another, who are not sure how many colour cards there are in a pack, how many cards in a suite and why the value of an Ace can vary between one and eleven!
For those children who are allowed to play cards `21s’ provides a very quick introduction.
Explain to your child that the aim of the game is to score 21 points.
An Ace is worth 1 or 11
The King, Queen and Jack are worth 10
Cards 2 to 10 are worth their face value.
Deal one card face down to each of players. Deal a second card face up.
Players are trying to get as close as possible to 21.
It is also possible to be a winner if one of the players reaches 21 with five cards.
The game can move along very quickly – but sometimes one or more player seems to take an age to make up his or her mind.
What happens, though, if your eleven plus child asks you: “Why is an Ace worth both one and eleven?”