An investigation involving adding and subtracting sets of consecutive numbers. Lots to find out, lots to explore.
Choose any three by three square of dates on a calendar page...
Can you create a Latin Square from multiples of a six digit number?
After every two numbers, one is omitted. Because $89 = 2\times 44 +1$, there must be $44$ page numbers missing and so the number on the last page is $89+44=133$.
This problem is taken from the UKMT Mathematical Challenges.