simple strategies for elementary math and work problems

This is a pretty good book. I will recommend a buy.

when you add many single digit numbers bucket them into 10s.

by 3 if you add all digits and they are divisible by 3

by 4 if it is even and the last 2 digits are divisible by 4

by 5 if it ends in 0 or 5

by 6 if divisible by 3 and 2

break them into factors. Start multiplying the largest factors first. Give an example for the kids.

multiply with a 10 or a multiple of 10 and half or double or triple

The story of check digits for addition, multplication, subtraction