Order of operations
Understand and apply the conventional order of operations (PEMDAS/BODMAS) to carry out calculations involving the four operations
What a learner can do afterwards
- Explain why 8 + 2 × 5 = 18 (not 50) by referencing multiplication before addition
- Evaluate a multi-step expression like 12 ÷ 3 + 4 × 2 correctly as 12
- State the correct order: brackets, then orders/exponents, then multiplication/division (L→R), then addition/subtraction (L→R)
1 · Read
A receipt adds up 8 + 2 × 5 to work out your shopping total. Get the order wrong and you could be charged the wrong amount. You already know brackets get solved first, but this problem has none at all, so working left to right won't give the right answer.
Look at 8 + 2 × 5. Multiply first: 2 × 5 = 10. Then add: 8 + 10 = 18. The answer is 18, not 50.
Now try 12 ÷ 3 + 4 × 2. Do the division and multiplication first: 12 ÷ 3 = 4, and 4 × 2 = 8. Then add: 4 + 8 = 12.
Multiplication and division always come before addition and subtraction. If there are two of the same type, work left to right.
Multiply and divide before you add or subtract, working left to right.
2 · Watch
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Where it sits
18 questions wait behind this lesson, each with its answer explained. Every answer feeds the sky: stars light as they are learned, and dim when it is time to come back.