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...
Investigate how you can work out what day of the week your birthday will be on next year, and the year after...
The number may be divided up into 400 blocks of '12345'. The sum
of the digits in each block is 15 and there are 400 blocks. Hence
the sum of all 2000 digits is 400 x 15 = 6000.
Alternatively, the mean of each group of five digits is 3 and so
the mean of the digits making up the number is 3. Therefore the sum
is 2000x3 = 6000.
This problem is taken from the UKMT Mathematical Challenges.