Fast Math in Ancient Egypt
Long before the calculator or even modern math, Egyptians had discovered a way to multiply large numbers quickly. Here’s how it works.
Suppose you had this problem: 13 x 12 =?
On a sheet of paper, draw a line to separate two columns. Down the column on the left, begin with the number 1. Double it and write 2 below it, and then double the 2 and write 4, and so on.
Down the column on the right, write the number you are multiplying by (in this case, 12). Under the 12, double it and write 24. Then double the 24 and write the number 48 under it, and so on.
Your columns should look like this:
| 1 | 12 |
| 2 | 24 |
| 4 | 48 |
| 8 | 96 |
| 16 | 192 |
Now find the numbers in the left column that add up to the first number in the problem (in this case, 13). The numbers 1 + 4 + 8 = 13, so underline the numbers in the right column opposite these numbers. Add these numbers (12 + 48 + 96), and you will get the sum 156, which is the correct answer to the problem of multiplying 13 by 12.
Now try another example: 38 x 251 =?
| 1 | 251 |
| 2 | 502 |
| 4 | 1,004 |
| 8 | 2,008 |
| 16 | 4,016 |
| 32 | 8,032 |
We see that 2 + 4 + 32 = 38. So 38 x 251 = 502 + 1,004 + 8,032. And that equals 9,538.
The ancient Egyptians also used columns like these to divide large numbers. Can you think of how they might have done that?
Source: highlightskids.com
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