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Sunday, January 13, 2013

Eleven Plus Probability

Early accounts of Australia told stories of men gambling with `Two Up’.  Two coins were tossed into the air and there were bets on the results. Some of the bets were small – but others were life changing.

If there were two heads the thrower won. With two tails the thrower lost. If there was a head and a tail then the throw was made again.

No self -respecting eleven plus parents would ever want to gamble with their child – but it could be an interesting way of a child learning about the laws of chance and probability. (Is playing for matches gambling?)

Questions on probability could, possibly, come up in the eleven plus. Consider a question along these lines:

You look at the boys and girls in your class of 25. Some are wearing glasses. You are asked to make an analysis.

No Glasses

The person sitting beside you is a girl. She wears glasses.
Nine people wear glasses so the probability of her wearing glasses is 9 out 25.
Only 4 boys wear glasses. This suggests 4 out of 9.

What is the probability of a girl wearing glasses?

What is the probability that the girl sitting beside you will be wearing glasses?

You could also explore probability using a table.

Probability is measured on a scale – where zero represents impossibility and one represents certainty.

Passing the eleven plus while asleep

Being either a boy or a girl





One coin landing either heads or tails