"What is 4 + 6 × 2?" The wrong answer is 20 (left-to-right). The right answer is 16 — because of BIDMAS, the order of operations. Every 11+ maths paper tests this; getting it wrong is one of the most common avoidable mark-losers.
What BIDMAS stands for
- Brackets
- Indices (powers and roots)
- Division
- Multiplication
- Addition
- Subtraction
(BODMAS is the same thing — Brackets, Orders, Division, Multiplication, Addition, Subtraction. Both are correct.)
The crucial rule about D-M and A-S
Division and multiplication have equal priority. You do them left-to-right. Same for addition and subtraction. So 12 ÷ 3 × 2 = 8 (not 2). And 10 - 3 + 2 = 9 (not 5).
Worked example
2 + 3 × (4 - 1)² = ?
- Brackets first: (4 - 1) = 3. Now: 2 + 3 × 3²
- Indices: 3² = 9. Now: 2 + 3 × 9
- Multiplication: 3 × 9 = 27. Now: 2 + 27
- Addition: 29. Answer.
Common 11+ BIDMAS traps
- Implied multiplication (3(2 + 1) = 3 × 3 = 9). The bracket is multiplied by the number outside.
- Negative numbers inside brackets ((-2)² = 4, but -2² = -4).
- Long expressions — work through methodically, don't try to do it all at once.
Practice that locks BIDMAS in
The trick is to do many short BIDMAS questions, not a few long ones. Quest Arena's maths worksheets include 40 BIDMAS drill sheets.