Talk:Primary Mathematics/Multiplying numbers

I have created a section for a description of the lattice method. I hope someone gets around to it before I do. It needs to be explained with graphics. As you can see, The standard algorithm needs to be further explained as well. It is important that the lattice method be included because it is used by many educators, and is a valid algorithm that finds its value in the service of differentiated environments. Though I have included a critisism of its "standardized" use, I see value in it as a way for students make the neccessary connections that will support their comfort with the standard algorithm. Multiplication with Decimals also needs to be addressed and I have made a heading for that. -Leightwing

Fabonacci demonstrated the jalousie method (a.k.a. lattice method) as a more refined version of the grid. For example:

The grid

| 200 | 70 | 5 | ======================= 50 ||    |    |   || --  2 ||     |    |   || ======================

Becomes the lattice

| 2 | 7 | 5 |  ================     /| / | / | / | 5    / |/  |/  |/  |   /  |---+---+---|   /  /|  /| / | / | 2 /  / | / |/  |/  | ===================

Multiply each pair, placing the digit in the tens value above the slash and the ones value below: | 2 | 7 | 5 |  ================     /|1/ |3/ |2/ | 5    / |/0 |/5 |/ 5|   /  |---+---+---|   /  /|0 /|1/ |1/ | 2 /  / | /4|/4 |/0 | ===================

Add the diagonals (each diagonal includes the numbers with a common place -- e.g. ones, tens, hundreds...) from left to right, carrying any tens to the next summation:

| 2 | 7 | 5 |  ================     /|1/ |3/ |2/ | 5    / |/0 |/5 |/ 5|   /  |---+---+---|   /  /|0 /|1/ |1/ | 2 /  / | /4|/4 |/0 | ===================     1   1  1  4   3  0  0

I think this improves on the grid method shown. In my opinion it demonstrates place values better and represents a simpler and more practical approach to solving the problem. Perhaps others find this method more confusing. If not the method, maybe others have a better gift for describing the method. I'll leave it to others to edit the module as they see fit.