Integers, BIDMAS& Directed Numbers.

What is BIDMAS and how does it work?

BIDMAS is the acronym used in IGCSE Edexcel Mathematics to define the order of operations — the sequence in which mathematical operations must be carried out to obtain the correct answer. The letters stand for:

• B — Brackets (work out expressions inside brackets first)
• I — Indices (evaluate powers and roots)
• D / M — Division and Multiplication (equal priority, left to right)
• A / S — Addition and Subtraction (equal priority, left to right)

A critical point that many students miss: Division and Multiplication are not separate levels. They share the same priority and are evaluated from left to right in the order they appear. The same applies to Addition and Subtraction. For instance, in the expression 12 ÷ 4 × 3, you work left to right: 12 ÷ 4 = 3, then 3 × 3 = 9 — not 12 ÷ 12 = 1.

How do directed numbers work in IGCSE Maths?

Directed numbers are numbers that carry a positive (+) or negative (−) sign. They appear throughout IGCSE Maths — in coordinates, algebra, temperature problems, and financial contexts. Mastering the rules for directed number arithmetic is essential.

Rules for adding and subtracting

• Same signs next to each other: Two positives or two negatives next to each other — replace with the appropriate single sign. E.g. 5 − (−3) = 5 + 3 = 8.
• Different signs next to each other: A positive and a negative next to each other become a minus. E.g. 5 + (−3) = 5 − 3 = 2.

Rules for multiplying and dividing

• Same signs → Positive result: (+) × (+) = (+), and (−) × (−) = (+).
• Different signs → Negative result: (+) × (−) = (−), and (−) × (+) = (−).
• The same rules apply to division.

Worked Examples

Common IGCSE Exam Mistakes

Exam Tips for Integers & BIDMAS