I found this partial mental arithmatic maths formula, for multiplying numbers in your head, on an old thread. I can only get it to work for numbers below 20. If someone can decipher it into a practical form, and get it to work for larger numbers, it would be a huge advantage when the calculator is out of arms reach.
This the original fragment,
Say 14 x 13...mutiply the 4X3 if theres any remainders then add that on to the total of 4+3 and add the first digits. So.. 4X3 = 12..3+4+1(carry the ten remainder)=8 and 1+1 =1 so equals 182
OR
14*13...4*3=12
............4+3+1=8 (1 is the remainder from the first line)
............1*1+0=1 (0 because 8 has no remainder)
=182
It sounds confusing, but work through it and it makes sense.
Post your results on this thread.
Cheers, Peach