7. Decimal operations

Lesson

The skills we have learned and used when adding whole numbers will be utilised once again when adding decimals. Let's review.

Find the value of 1832 + 6361.

Worked Solution

Idea summary

We can add large numbers using a vertical algorithm. We add the digits starting from the lowest place value and move left.

This video shows us how to add numbers with decimals.

Find 0.17+0.52 giving your answer as a decimal.

Worked Solution

Idea summary

When adding decimals using a vertical algorithm, we must make sure to align the decimal points. If the decimals have a different number of decimal places, then we can use zeros as place holders.

What if our numbers get larger but still have decimals? The same strategies still apply, this video shows us.

Find 13.74+37.26 giving your answer as a decimal.

Worked Solution

Idea summary

We can add larger decimals using the vertical algorithm. It will just require more steps.

When adding decimals we can use regrouping in the same way that we use it when adding whole numbers.

This video shows us how to continue patterns with decimals.

Consider the following pattern.

0.03, \ 0.12, \ 0.21, \ ⬚, \ ⬚, \ ⬚

a

Complete the pattern.

Worked Solution

b

What is the pattern?

A

The numbers are increasing by 0.09.

B

The numbers are increasing by 90.

C

The numbers are increasing by 9.

D

The numbers are increasing by 0.9.

Worked Solution

Idea summary

To complete a pattern of decimals, it may help to write the numbers as tenths, hundredths or thousandths or as fractions to see how the pattern changes each time.

Add and subtract decimals, with and without digital technologies, and use estimation and rounding to check the reasonableness of answers