How_To_Be_Good_At_Math

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CALCULATING • MULTIPLYING DECIMALS

We can use long multiplication to multiply decimals.

It might look tricky, but really it’s just as simple as

multiplying any other number. All we have to do is

make sure we carefully line up the decimal point in

the answer line with the decimal point in the question.

Multiplying decimals

Next, multiply 6 by 2. The answer

is 12. Write 2 in the next column to

the left of the decimal point, and 1 in the

next column.

Let’s multiply 6.3 by 52.

First, write the number with the

decimal number above the whole

number. We don’t need to line up the

numbers according to their place values.

Write a decimal point on a new line,

below the decimal point in the question.

Now we’re going to multiply each of

the digits on the top row by each digit

on the bottom row. Start by multiplying all

the digits by 2.

First, multiply 3 by 2. The answer is 6.

Write 6 in the first column.

We don’t need

to line up the

numbers by

place value

Line up this

decimal point

with the one in

the question

We’ll multiply

each digit on the

top row by 2

Write the 6 here

Multiply 3 by 2

Multiply 6 by 2

6.3 × 52 =?

.

.

.6

When multiplying with

decimals, it helps to

estimate the answer first,

so you can see at the end

if you’ve made a mistake.

6.3

52

6.3

52

6.3

52

12 .6

6.3

52

124-125_Multiplying_decimals.indd 124 29/02/2016 18:56