Make a set of numbers that use all the digits from 1 to 9, once and
once only. Add them up. The result is divisible by 9. Add each of
the digits in the new number. What is their sum? Now try some other
possibilities for yourself!
Calculation 2000
Age 11 to 14 Short Challenge Level
What is the value of $2000+1999 \times 2000$?
If you liked this problem, here is an NRICH task which challenges you to use similar mathematical ideas.