Lesson

Let's try a practice problem to remember how patterns can help us with addition and subtraction.

Fill in the boxes with the missing numbers.

a

14+5=⬚

Worked Solution

b

24+5=⬚

Worked Solution

c

34+5=⬚

Worked Solution

d

84+5=⬚

Worked Solution

e

What is the pattern? Choose the correct answer:

A

When you add one number to another, the answer becomes smaller.

B

When adding 5 to a two-digit number that ends in 4, we get a two-digit number that ends in 9.

Worked Solution

Idea summary

We can use number lines and patterns to add numbers together.

12-4=8. Use this to find:

a

22-4=⬚.

Worked Solution

b

32-4=⬚.

Worked Solution

c

42-4=⬚.

Worked Solution

d

72-4=⬚.

Worked Solution

Idea summary

To add or subtract using patterns, compare the calculation that you are trying to work out to another calculation that you already know. If you can see a pattern between the numbers, then you can use that to find the answer.

Sometimes our problem is in the form of a story, or sentences. In this video, we see how to work out our number problem from the key words, or clues.

Four friends are picking fruit in an orchard. Tricia picks 16 apples, Ryan picks 29 peaches, James picks 23 pears and Laura picks 15 plums.

How many pieces of fruit were picked in total?

Worked Solution

Idea summary

There are some words we might come across that mean we will be using addition whereas other words may suggest subtraction. This is not a complete list, so we need to understand the context of the question, to work out whether to add or subtract.

addition | subtraction |
---|---|

more | less |

longer | shorter |

later | earlier |

bought | sold |

joined | left |

Use efficient mental and written strategies and apply appropriate digital technologies to solve problems

Describe, continue and create patterns with fractions, decimals and whole numbers resulting from addition and subtraction