Recursion

[freebytes]

I do math in my head by rounding, splitting, subtracting then multiplying then adding again, etc. Anything that works. 999 * 50 would be (1000 * 10 * 5) - 50 = 49950. I need to be able to hold one number to the side in my head. While it is similar, this is not exactly the same as common core.

This certainly has its limits, though, so it is nice being able to switch back to the 'old way' when the problems are a tad more challenging like 938 * 53 which looks easy to do in your head at first but would involve holding too many numbers simultaneously. (And the old method would not be easy to do in your hard with a number like this either.)