Topic Four (1.4): Mental methods of addition and subtraction
Introduction
There are many methods to help you add and subtract numbers in your head. This section looks at the partitioning method, which splits numbers into parts, and the compensation method, which allows you to adjust a number to make the sum easier.
Working through your course book
- Go to the MyMaths 1B digital book and watch the video on page 11.
- Read page 10, which gives examples of how partitioning is used to help, along with the compensation and the difference method.
- Check your understanding by answering the questions on page 11.
- If you would like more practice, then work through these lessons on the MyMaths website:
You may also want to watch the following MathsWatch videos and work through the interactive questions using the tab at the top of the screen:
WATCH - Adding numbers mentally (MathsWatch) Links to an external site.
WATCH - Subtracting numbers mentally (MathsWatch) Links to an external site.
For a further explanation on the use of compensation:
WATCH - Compensation Strategy - Mental Math (Madly Learning - YouTube) Links to an external site.
And for a further explanation on the use of partition:
WATCH - Mental Addition - Partitioning (KSAMathematics - YouTube) Links to an external site.
Support activities for this topic
The MyMaths 1A digital book introduces the basic skills for mentally adding and subtracting tens and units. If you'd like to take more time to understand these, look at pages 130-133 for more support.
Extension activities for this topic
The MyMaths 1C digital book provides extension material in their problem-solving questions.
If you would like more of a challenge on this topic, go to page 11 of the MyMaths 1C digital book and attempt questions 5 and 6.