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
1 · Read
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. Without brackets, × comes before +, so 8 + 7 × 2 would mean 8 + 14.
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, look at their parts. If both repeat the same bracket, the one that repeats it more times is larger. If both repeat it the same number of times, the one with the bigger amount inside the brackets is larger.
A number sentence records a calculation in symbols, and you can often read what it means without working out the answer.
Readings 'Doing the steps in order', 'Letting the words place the brackets', 'Comparing without calculating' and 'Four batches of pancakes' are original to this dataset. All 10 extra questions are original to this dataset.
2 · Watch
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18 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.