Stage: 2 Challenge Level: 
There was a great deal in this problem and James has answered part of it:
Using only three rods with each one not exceeding 10 you can add and minus the following numbers which can go from 1-13.
The three numbers are 9, 3 and 1.
| 1 | = | 1 |
| 2 | = | 3-1 |
| 3 | = | 3 |
| 4 | = | 3+1 |
| 5 | = | 9-3-1 |
| 6 | = | 9-3 |
| 7 | = | 9-3+1 |
| 8 | = | 9-1 |
| 9 | = | 9 |
| 10 | = | 9+1 |
| 11 | = | 9+3-1 |
| 12 | = | 9+3 |
| 13 | = | 9+3+1! |
Well done James. Is 13 the largest number and why?
Can any of you help with some of the rest of the question:
In how many ways can you make 10?
What is the maximum number you can make with 4 rods?
Perhaps you can send in some more ideas.
Addition & subtraction. Combinations. Interactivities. Trial and improvement. Investigations. Generalising. Place value. Multiplication & division. Factors and multiples. Working systematically.
Published December 2001.
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