How_To_Be_Good_At_Math

126 CALCULATING •^ THE LATTICE METHOD

The lattice method

There are several ways to do multiplication calculations,

as you have seen. The lattice method, shown here, is very

similar to long multiplication, but we write the numbers out

in a grid instead of columns. We can use the lattice method

for large whole numbers, and numbers with decimals.

Extend the

diagonal beyond

the edge of the

lattice

Write the ones

below the line

Write the product

in each box

Write the tens

above the line

The lattice method

can be used for

whole numbers

and decimals.

Let’s multiply 78 by 64 using

the lattice method.

Next, multiply the digit at the top of

each column by the digit at the end

of each row. When we multiply 7 by 6, the

answer is 42. Write 4 in the top of the box

and 2 in the bottom of the box. We are

separating the product into its tens and ones.

The numbers in our calculation are

both two digits long, so we draw a grid,

or lattice, that is two boxes long and two

boxes tall. Write the numbers in the

calculation along the edges of the lattice.

Now, draw a diagonal line through each

box from the top right to the bottom left.

The numbers that we are going to write along

each diagonal will have the same place value.

6

4

7 8 ×

6

4

7 8 ×

6

4

(^78) ×
4
2
78 × 64 =?
Continue multiplying the numbers at the
top of each column and the end of each
row until all the boxes are filled.
6
4
(^78) ×
4
2 3
4
2
(^82)
8
126-127_The_lattice_method.indd 126 29/02/2016 16:39