Multiplying large numbers - lattice method - 1

This method is also called Napier's bones. In some ways it is similar to the grid method as it involves multiplying rows and columns, but it gives you a better way to add the results at the end of the calculation.

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:
25 x 5

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

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

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

25 x 5 = 125

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!