How_To_Be_Good_At_Math

62 NUMBERS •^ ADDING DECIMALS

Adding decimals

We add decimals in the same way as we add whole numbers –

turn to page 87 to find out the written way to add decimals.

First, let’s add

the tenths from the

two numbers: 0.5 + 0.7.

This gives us^12 ⁄ 10 , or 1.2.

Let’s add 4.5 and

7.7. To help us see

how adding decimals

works, we’ll show the

calculation using

counting cubes.

Now let’s add

the two whole

numbers, 4 and 7,

together to make 11.

Now we can

add our two

answers, 1.2 and 11,

together to get the

final answer, 12.2.

We have found that

4.5 + 7.7 = 12.2.

When we write the

calculation, it looks like

this – go to page 87 for

more about adding

decimals in this way.

Each light blue block is one tenth

We exchange ten one

strips for one ten block

We exchange ten tenth

cubes for a ones strip

A dark blue strip is one, made up of ten tenths

We have one ten, two

ones, and two tenths

4.5

1 2 .2

4.5 + 7.7 =?

or 0.5 + 0.7 = 1.2

or 4 + 7 = 11

= or 11 + 1.2 = 12.2

• 
  

  =

  
  


• 
  

  =

  
  

so 4.5 + 7.7 = 12.2

• or=?

4.5 7.7

0.5 0.7 1.2

4 7 11

11 1.2 12.2

1

T O 101

7 .7

062-063_Adding_Decimals.indd 62 29/02/2016 14:09