BIDMAS
- Calculations must be done in the right order: Brackets, Indices (powers and roots), Division and Multiplication, Addition and Subtraction.
- Division and multiplication have the same priority: work from left to right. The same applies to addition and subtraction.
Examples
- 3 + 4 × 2 = 3 + 8 = 11 (multiply first).
- (3 + 4) × 2 = 7 × 2 = 14 (brackets first).
- 18 ÷ 3 × 2 = 6 × 2 = 12 (left to right).
- 2 + 3² = 2 + 9 = 11 (indices before addition).
Fractions and calculators
- A fraction bar acts like brackets: (12 + 8) ÷ (6 − 1) can be written as a fraction with 12 + 8 on top.
- Scientific calculators follow BIDMAS, so use brackets when you type in calculations like (5 + 3) ÷ 2.
Common mistakes
- Don't just work from left to right: 10 − 2 × 3 is 4, not 24.
- 5 × 2² = 5 × 4 = 20, not 10² = 100.
Key terms
- BIDMAS
- The order of operations: Brackets, Indices, Division/Multiplication, Addition/Subtraction.
- Indices
- Powers and roots, such as squares and square roots.
- Operation
- A mathematical process, such as adding or multiplying.
- Priority
- Which operation is done first.