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Answer: 133
Printing Error
Age 11 to 14
ShortChallenge Level 
Answer: 133
| page | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 |
| number | 1 | 2 | 4 | 5 | 7 | 8 | 10 | |||
| = | = | +1 | +1 | +2 | +2 | +3 | +3 | +4 | +4 |
Add one to the difference for each odd page
89 is before 90, the 45th even number, so 89 is the 45th odd number
Difference has increased by 1 for every odd number except for 1
So number 89 + 45 = 133 is printed on the last page.
This problem is taken from the UKMT Mathematical Challenges.
You can find more short problems, arranged by curriculum topic, in our short problems collection.
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