This topic summary covers Knowledge Organiser: BIDMAS within BIDMAS for GCSE Mathematics. Revise BIDMAS in Number for GCSE Mathematics with 14 exam-style questions and 22 flashcards. This topic appears regularly enough that it should still be part of a steady revision cycle. It is section 9 of 9 in this topic. Use this topic summary to connect the idea to the wider topic before moving on to questions and flashcards.
Knowledge Organiser: BIDMAS
Key Terms
- BIDMAS: Order of operations — Brackets, Indices, Division, Multiplication, Addition, Subtraction
- Brackets: Always solved first, including nested brackets (inside out)
- Indices: Powers and roots, solved second
- Equal priority: Division and Multiplication have equal rank; so do Addition and Subtraction
- BODMAS: Alternative name — Orders instead of Indices
Must-Know Facts
- Multiplication does NOT always come before division — they are equal priority
- When two operations have equal priority, work left to right
- 12 ÷ 3 × 2 = 8 (not 2) — left to right rule
- 2 + 3 × 4 = 14 (not 20) — multiplication before addition
- Nested brackets: solve innermost first, then work outwards
- Indices apply to whatever is directly to their left (use brackets to extend scope)
BIDMAS Order
- B — Brackets first
- I — Indices (powers/roots)
- D/M — Division and Multiplication (left to right)
- A/S — Addition and Subtraction (left to right)
- Memory: "Big Elephants Destroy Many Ant Settlements"
Common Mistakes
- Multiplication before division: They have equal priority — always work left to right when both appear
- 2 + 3 × 4 = 20: Wrong! Multiply first: 2 + 12 = 14
- Ignoring nested brackets: Solve innermost brackets first, not outermost
- Indices scope: 2 × 3² means 2 × 9 = 18, not (2×3)² = 36 — indices only apply to what is directly to their left
- Addition before subtraction: They are equal priority — work left to right
Practice questions for BIDMAS
What does the letter 'I' stand for in BIDMAS?
Explain what BIDMAS tells us about calculations and why it is needed.
Quick recall flashcards
Calculate: 10 - 2²
**Step 1:** Indices first (BIDMAS)
2² = 4
**Step 2:** Then subtraction
10 - 4 = **6**
*(Not 10 - 2 = 8, then 8² = 64)*
Calculate: 2 + 3 × 4
**Step 1:** Multiplication first (BIDMAS)
3 × 4 = 12
**Step 2:** Then addition
2 + 12 = **14**
*(Not 2 + 3 = 5, then 5 × 4 = 20)*