How_To_Be_Good_At_Math

118 CALCULATING •^ EXPANDED LONG MULTIPLICATION

Expanded long

multiplication

When we need to multiply two numbers that both have two or more digits,

we can use a method called long multiplication. There are two main

ways to do it. The method shown here is called expanded long multiplication.

The other method, called long multiplication, is shown on pages 120-23.

Let’s multiply 37 by 16 using expanded

Long multiplication

Start by writing the two numbers out

like this, with digits that have the

same place values lined up one above

the other. It might help you to label the

place values, but you don’t have to.

Now we’re going to multiply each of

the digits on the top row by each of

the digits on the bottom row. We’ll start by

multiplying all of the digits on the top row

by 6 ones.

First, multiply 7 ones by 6 ones.

The answer is 42 ones. On a new

line, write 4 in the tens column and 2

in the ones column.

37

16

Write the

numbers so

that the digits

with the same

place values are

lined up like this

H T O

×

Next, multiply 3 tens by 6 ones.

The answer is 18 tens, or 180.

On a new line, write 1 in the hundreds

column, 8 in the tens column, and

0 in the ones column.

We’re going to

multiply each digit

on the top row by 6

Write the answer

on a line below

37

16

Multiply 3 tens

by 6 ones

H T O

×

42

180

37 × 16 =?

37

16

H T O

×

37

16

H T O

×

42

Multiply 7 ones

by 6 ones

118_119_Expanded_long_multiplication.indd 118 29/02/2016 14:11