Writing Number Sentences
Write simple numerical expressions that record calculations with numbers, and interpret numerical expressions without evaluating them (e.g. recognise that 3 × (18932 + 921) is three times as large as 18932 + 921)
What a learner can do afterwards
- Write an expression for 'add 8 and 7, then multiply by 2' using parentheses
- Explain what 4 × (365 − 12) represents without computing it
- Compare two expressions and determine which is larger without evaluating
The lesson
A number sentence turns words into math symbols. It uses numbers, operation signs like + and ×, and sometimes brackets to show what to work out first.
Marcus hears: 'Add 8 and 7, then multiply by 2.' He writes it as (8 + 7) × 2. The brackets keep 8 + 7 together, so that part happens first.
You can also read a number sentence without solving it. Look at 4 × (365 − 12). The × 4 out front tells you the whole bracket amount is repeated four times, so the answer is four times as large as 365 − 12.
To compare two number sentences without solving them, check if they repeat the same group a different number of times, or if the group itself is a different size.
A number sentence records a calculation in symbols, and you can often read what it means without working out the answer.
Watch it
Where it sits
Learn first
This opens up
8 questions wait behind this lesson, each with its answer explained. Every answer feeds the sky: stars light as they are learned, and dim when it is time to come back.