I have watched quite a few videos over the year, Mr. Gillespey, and all of them have proved useful during tests and competitions. Thank you for providing us with these tips!

Assuming that the first digit of two numbers are equal and the two second digits add up to 10:
1. Multiply the last digit times the second last digit. If there is one digit,
put a zero before the digit.

2. Add 1 to one of the first digits and multiply the other first digit times that +1 digit.

## 2 comments

I have watched quite a few videos over the year, Mr. Gillespey, and all of them have proved useful during tests and competitions. Thank you for providing us with these tips!

Assuming that the first digit of two numbers are equal and the two second digits add up to 10:

1. Multiply the last digit times the second last digit. If there is one digit,

put a zero before the digit.

2. Add 1 to one of the first digits and multiply the other first digit times that +1 digit.