Specific Tricks Level 6: Complementary ones (hard, tens 7-9). complementary ones product.
1. Ones make ten
1.
Confirm that the two ones digits total 10.
2. Front product
2.
Multiply the tens digit by its next integer.
3. Ending product
3.
Multiply the ones digits and keep two ending digits.
4. Read answer
4.
Join the front and two digit ending, then read the product.