[Young Werther]

My 4th grade math teacher taught us the "code" using numbers ending in 5 as a starting point.

15 X 15 = 1 X 2, (first digits) and 5 X 5 = 25. therefore 15 X 15 = 225.

45 X 45 = (4X5=20) and (5X5=25) so 45X45=2025.

Other numbers work as well. For example 33 X 33= (33+3=36X3=108) and (3X3=9)so 33X33=1089! TA DAH

Today I use Excel, Cell Phone and other electronic devices which are as accurate and cost less than $33 for the "copyrighted formula"!

[rawhide]

Interesting. Does this work only with numbers ending in 5?
How about 95x95?

I also multiplied 87x36 using your formula, and I cannot get it to come out to the correct number?

[green pastures]

I couldn’t tell from your example how you picked the multiplier for the first digits.

1x2, 4x5... How do you know the multiplier for the first digits?

Also didn’t follow the example for using it for other numbers.