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?
How many 2010-digit numbers are there in which every pair of consecutive digits forms a two digit number that is divisible by $17$ or $23$?
If you liked this problem, here is an NRICH task which challenges you to use similar mathematical ideas.
This problem is taken from the UKMT Mathematical Challenges.