Maths · Order of operations
BIDMAS Machine
Work the expression out one operation at a time. Tap the operation that has to happen next.
Free to use and free to share. There is no sign-up, no score, and nothing a child does here is recorded or sent anywhere. What you may do with it, in full.
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Why this works
Brackets come first, so before anything else happens. That leaves the rest of the line to finish, and comes to 81. Reading it straight from left to right gives 144 instead, which is why the order is the whole question.
Helping a child through BIDMAS Machine
Hints, least revealing first
- Anything inside brackets is a parcel. It has to be opened before the rest of the line can move.
- Multiplying and dividing happen before adding and subtracting, however far along the line they sit.
- Reading straight from left to right gives 144, which is not the same thing.
When they finish it: “Worked out in the right order.”
What usually goes wrong here
- Evaluates every operation from left to right.
This is the wrong answer 11+ papers are built to offer, so it is worth watching for directly: a child who does this will look confident and still lose the mark. If it keeps happening on evaluate a mixed expression, the fix is the misunderstanding rather than more questions.
2 11+ skills this exercise practises
Each of these has its own page, with a worked example on it. 1 of the 2 names the mistake that skill attracts.
- Calculate a whole-number operationCalculate one stated addition, subtraction, multiplication, or division.
- Evaluate a mixed expressionApply operation order to a supplied numerical expression.
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One exercise is a start, not a plan
A free diagnostic across all four subjects shows which maths skills to practise next, and in what order.