Copyright © University of Cambridge. All rights reserved.
'Odds or Sixes?' printed from https://nrich.maths.org/
Odds or Sixes?
Tania and Derek are playing a game with a dice.
They roll the dice. If the number is odd, Tania wins that round.
If the number is a six, Derek wins.
(It doesn't matter who throws the die.)
Who is more likely to win the game? Why? How could you make the game fair?
Why do this problem?
This problem gives learners the opportunity to describe and predict outcomes, and consider the meaning of 'fair'.
Possible approach
You could introduce this problem either by having two children come to the front to play it. Whichever way you choose, play the game a few times and record the outcomes on the board. Ask the class to predict what would happen if the game was played many times, for example $100$ times. Take suggestions from the children, looking out for those who justify their answer based on the few games
which have already been played.
Suggest that the group tests out their theories. This could be done by pairs throwing dice and then collating class results. Bring pupils together to talk about their findings and ask them whether the game is fair or not and why. Listen out for explanations which compare the number of possible winning throws using appropriate vocabulary. Some children might quantify the probability of
throwing a six, for example, as $1$ out of $6$ or $\frac{1}{6}$ whereas throwing an odd number is $3$ out of $6$, or $\frac{1}{2}$.
It would be useful to encourage children to talk in pairs about what they understand as 'fair' - there will be different, but equally as valid, ideas about how to change the game.
Key questions
What numbers are possible to throw on the dice?
Who would win with each number?
Can you use this to decide how to make the game fair?
Possible extension
Learners could try
Odds and Evens which extends the ideas in this problem.
Possible support
Having dice available will help those children who are not familiar with them and playing the game for themselves would also be of benefit.