Skillswise Factsheet
N1/L1.3
N1/L1.5

Multiplying large numbers - lattice method - 2

Here's another multiplication sum worked out using the lattice method.
With this method, you multiply each number in the column by each number in the row. Then you add along the diagonals to get the answer.

Have a look at this sum:
255 x 25

Step 1.
Make a grid with diagonal lines as shown below. Split the 255 into 2, 5 and 5, putting each digit at the top of a column. Split the 25 into 2 and 5, putting each digit by a row.

Lattice method step 1

Step 2:
Multiply the columns by the rows, splitting the digits up on either side of the diagonal as shown here.

Lattice method step 2

Step 3:
Finally, add along the diagonals to get your answer.

Lattice method step 3

255 x 25 = 6375

This method is a bit complicated. Talking yourself through each step as you do it can be useful - someone is sure to ask you what you're doing and you'll end up explaining to them!


You can find Skillswise at http://www.bbc.co.uk/skillswise
This factsheet is BBC Copyright