How can two decimals so ugly make one so beautiful?

I am learning to add decimals.

Callum has 1.7 chocolate bars and Sue has 1.3 chocolate bars how much do they have in total?

Callum has 1.7 Sue has 1.3

1.7 + 1.3 = ?

Let’s combine the tenths. Now combine the wholes.

You can see that the 7 tenths (0.7) and the 3 tenths (0.3) combined to make 1 whole.

1.7 + 1.3 = 3

Susan has 2.8 chocolate bars and Alice has 1.2 chocolate bars how much do they have in total?

Susan has 2.8

Alice has 1.2

2.8 + 1.2 = ?

Let’s combine the tenths. Now combine the wholes.

You can see that the 8 tenths (0.8) and the 2 tenths (0.2) combined to make 1 whole.

2.8 + 1.2 = 4

Now let’s try a question with hundredths.

Andrew has 1 chocolate bar and 6 hundredths. Zane has 1 chocolate bar and 4 hundredths. How much do they have in total?

Remember there are ten hundredths in a tenth and one hundred hundredths in 1 whole.

Andrew Zane1.06 + 1.04 = ?

Combine the hundredths. Combine the wholes. 1 + 1 = 20.6 + 0.4 = 1

1.06 + 1.04 = 2.1

Now let’s try one with wholes, tenths and hundredths.

Taine has 1.78 and Jonah has 1.22. How much do they have in total?

Taine Jonah

Combine the hundredths. 0.08 + 0.02 = 0.1 Let’s move this tenth up with the other 7.

Combine the tenths. 0.7 + 0.1 + 0.2 = 1.0

Made from the hundredths

Combine the wholes. 1 + 1 + 1 = 3

Made from the tenthsSo… 1.78 + 1.22 = 3

Now try these questions on your own.

1) 2.5 + 3.5 =

2) 2.9 + 4.1 =

3) 5. 3 + 2.7 =

4) 6.4 + 2.6 =

5) 3.2 + 2.8 =

Click again when you have worked out all your answers.

Need some more practise? Try Teacher Tools Fractions, Decimals and Percentages Book Numeracy resources

6) 5.02 + 2.08 =

7) 3.03 + 2.07 =

8) 5.01 + 2.09 =

9) 2.44 + 1.56 =

10) 1.83 + 1.17 =

6

7

8

9

6

7.1

5.1

7.1

4

3