Lattice Multiplication

I’m going to bleed a little in this post because it’s about something very dear to me: Mathematics.

I got held back in math in second grade.  I remember walking to class and seeing my teacher holding the book for the lower level math class.  I’d been struggling in math and I immediately got this pit in my gut fearing what was about to happen and, sure enough, she called me over to her and escorted me to the lower level math class.  I don’t remember much after that…

Well I was recently on an interview and my interviewer kept saying, “This is just like you learned how to do multiplication in third grade!” and kept pressing me to implement a solution in that multiplication view.  Unfortunately for me, my brain ceased.  I flashed back to being a kid again and being escorted to that lower level math class.  If I don’t get the position I suspect that— response of mine will be a big factor why.

Thing is, I can do multiplication by hand.  Just in order for me to do it I have to change what it looks like cause, and it was actually in third grade, that I learned about Lattice Multiplication.  You go through all the motions of multiplication yet but, you change what it looks like and that change in visual has allowed me to do things like get through the math section on the GRE so I stand by it. I’ve no doubt that there are other walkthroughs on the Internet but this is important to me and I would like to personally try and help keep other children (and adults) from being haunted by math.  Math isn’t scary.  But how to do it isn’t one method fits all.

Lattice Multiplication is like this:  First you draw a grid, one box for each number you’re going to need to multiply, and split the squares on the diagonals:

grid1

Then write your numbers you need to multiply.

grid2

In the “third grade” way this would be:

279
 84
---
  ?

Now you multiply.  Right to left across rows and down columns.  The number in the 10’s position goes in the upper part of the diagonal split cell, and the 1’s in the lower.grid3

Then you begin to add down the diagonals.  If you have a carry (blue circled numbers), simply put it at the top of the next diagonal and add it as well.

grid4

Then you just read your answer along the bottom (blue arrow).

grid5

As with the “third grade” method I was being required to use, as long as your basic multiplication tables are known, you’re then able to approach multiplication this way.  Well actually it’s the same way only you don’t have to worry about indentation in the result and this way doesn’t remind me of past events so I was able to do things like survive the GRE.  It’s amazing what a change in perspective allows you to do or see sometimes.

If you’re struggling with multiplication, I recommend giving this a go.  It has worked for me.