How did ancient egyptians multiply numbers?

painting by the Austrian artist Franz Miklis


A really cool thing I've read in a restroom in the public library, while sitting there.

"Suppose you're and old Egyptian and you wanna multiply 36 · 43. Remember that you don't have the zero. What can you do? Do the following: Take one of the two numbers, and factorize it out (row (a)); then, take the other number and double it as many times as steps your factorization in row (a) took (do this in row (b)). Finally, add up the numbers in row (b) that have the same step number of an odd number in row (a). For example, if step (iii) in row (a) contains a 10, which is even, then don't add up the number in step (iii) in column (b). Do the addition in row (c). Look at the example we started with, i.e. 36 · 43. Let's factorize the number 43, and double 36 as many times as steps the factorization of 43 has (i.e. 6 times, in this case):

ROW A: (i) 43 ; (ii) 21 (forget about the residue) ; (iii) 10 ; (iv) 5 ; (v) 2 ; (vi) 1

ROW B: (i) 36 ; (ii) 72 ; (iii) 144 ; (iv) 288 ; (v) 576 ; (vi) 1,152

ROW C: (i) 36 + (ii) 72 + (iv) 288 + (vi) 1,152 (we don't add steps (iii) and (v) of row (b), because steps (iii) and (v) in row (a) contain an even number).

That is row (c) amounts to the following addition: 36 + 72 + 288 + 1152 = 1,548.

Do the math, and check that this result is correct, i.e. that 36 · 43 = 1,548.
Try the system with any other numbers."

Isn't it awesome?