another approach might be to treat numbers as letters, squaring them is then rep...

		signa11 on March 29, 2010 \| parent \| context \| favorite \| on: Squaring two digit numbers in your head another approach might be to treat numbers as letters, squaring them is then represented algebraically as (a+b) ^ 2 == a^2 + b^2 + 2ab which can then be easily combined: 79^2 = 49, 126, 81 => 6241 a == 7, a^2 == 49 b == 9, b^2 == 81 2ab == 279 = 126 combination == (a^2+2ab+b^2) from 81 take 1 add '8' to 2ab == 134, take 4 add '13' to 49 == 62 answer == 6241

I do that for all 2 digit multiplication I do in my head- I just use foil.