Multiplication with Lines

demakinz

I came across this method of multiplication on youtube the other day. You can multiply numbers by drawing lines on a page horizontal and vertical and counting the intersections.

Iv tested it with a few different number and it seems to work every time. I asked my math tutor in college about it but he never seen it before he seemed surprised when it worked.

Has any of you guys seen this before or know where it comes from? Does it work with every number I wonder im sure there must be some limitations. I had fun showing my friends this:D

https://www.youtube.com/watch?v=sd_Bub5jEJY

hivizman

This is basically the same as the method of "long multiplication" that we used to employ before the introduction of calculators. To take the example given in the video, multiplying 321 by 123, you would begin by multiplying 321 by 100, then multiply 321 by 20 and finally 321 by 3 and add the three numbers together. The calculation would look like this:

321

123

x

32100

6420

963

39483

Some people were taught to omit the final zeroes (e.g. in 32100 and 6420), just making sure that the numbers lined up properly in the thousands, hundreds, tens and units columns.

Counting the intersections of the lines gets very messy for higher digits, and you are more likely to make errors.