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Class 7 Arithmetic Expressions: cheat sheet
CBSE Mathematics. An expression is a sum of terms. Brackets and the order of operations decide what to work out first; rearranging terms makes sums easier.
Key ideas
- Work out brackets first, then multiplication and division from left to right, then addition and subtraction from left to right.
- Every expression can be read as a sum of terms: 30 − 8 + 5 has terms 30, −8 and +5.
- Terms can be added in any order and grouped in any way without changing the value.
- A minus sign before a bracket changes the sign of every term inside it.
- Compare two expressions by seeing which terms differ, without working out both.
Remember
| Removing a bracket after a minus | a − (b + c) = a − b − c; a − (b − c) = a − b + c |
| Distributing | a × (b + c) = a × b + a × c |
| Example | 194 − 35 + 37 − 38 = (194 + 37) − (35 + 38) = 231 − 73 = 158 |
Watch out
- Working strictly left to right and ignoring brackets or multiplication.
- Changing the sign of only the first term after a minus bracket.
- Treating subtraction as if the order did not matter: 10 − 3 is not 3 − 10.
Worked example
Find 194 − 35 + 37 − 38.
Working: add the positive terms 231, subtract 73
Answer: 158
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