This game is about subtraction.
All players start on 100 (or 20 if necessary), and roll either 20 sided or 10 sided dice to give them a score. They then take this away from their 100. They will start with this new score in their second round, and that new score in the third round etc.
The aim is to reach zero. Some children will gamble near the end, and may end up going 'bust'. Or they can freeze if they think they can't get a better low score without going bust.
Here are Daniel and Chloe to talk you through an example game:
What to listen for / look out for:
- use of number bonds:
- they may know that 80-7 = 73, because they know that 7 and 3 make a number bond of 10;
- this is useful for taking away scores of more than 10, for example to take 16, children may want to take 6 first and then 10, or take 10 first and then 6;
- for many children this will be their 'default' strategy, so be aware that if they could use a more appropriate method, you might need to insist that they do. See the two methods below for more detail;
- bridging method:
- this is perfect for situations like this: 83 - 15
- Since partitioning does not make this problem that much easier, a more appropriate method will be to 'bridge' to the nearest multiple of 10 first.
- In this case, 83 - 3 = 80. Now that we have already taken away 3, we only have 12 left to take away. Now we can say we have the problem: 80 - 12
- From here, children are usually happy to use partitioning and number bonds to answer.
- round and adjust method:
- Sometimes, when we have numbers that are 'nearly numbers', they are easier to just treat them like what they are near to. For example, 7 is nearly 10, as are 8 and 9. Likewise 17 is nearly 20, as are 18 and 19.
- We can use this to make calculations with subtracting 17 a lot easier. So, instead of 74 - 17, we will round 17 to 20, and then take this away instead: 74 - 20 = 54.
- Is this fair? Not at all. Children should be encouraged to point out that it isn't fair, as if they do take 20 away, the score is lower than it should be... by 3 in fact.
- At this point, children then add those 3 back on to make: 54 + 3 = 57. This is the part we call adjusting.