Apply BEDMAS to rational numbers including fractions and decimals. Grade 9 Alberta math lesson.
Lesson 3.6 of Rational Numbers in Grade 9 Math — Alberta curriculum lessons.
When solving math problems, you can't just go left to right — there's a specific order that must be followed.This order is called BEDMAS, which stands for:
⚠️ Important. • Division and multiplication are done in the order they appear, left to right.• Addition and subtraction are also done left to right.
Even when you know the BEDMAS rule, small mistakes — like skipping brackets, forgetting to square a term, or doing steps in the wrong order — can completely change your answer.
In this section, we'll look at two examples with decimals and fractions, see where students went wrong, and learn how to fix them step-by-step.
Problem:Evaluate(−2.4) + 1.2 − 7 × 0.2Two students tried this question but got different answers.
(−2.4) + 1.2 − 7 × 0.2= (−2.4) + 1.2 − 1.4= (−2.4) + (−0.2)= −2.6
(−2.4) + 1.2 − 7 × 0.2= (−2.4) + 1.2 − 7 × 0.2= (−2.4) + (1.2 − 7) × 0.2= (−2.4) + (−5.8 × 0.2)= (−2.4) + (−1.16)= −3.56
❌ Incorrect. Student 2 did the subtraction before multiplication instead of following BEDMAS.Multiplication must always come before addition or subtraction.
Problem:Evaluate(−22) × 11 + 11Two students got different answers — only one followed BEDMAS correctly.
When working with decimals or fractions, always remember:
🔑 Important Rules.
Now it's your turn! Look at these two students' work and determine who followed BEDMAS correctly.
Question: (−2.4) + 1.2 − 7 × 0.2Step 1: Do multiplication first.7 × 0.2First ignore the decimal: 7 × 2 = 14Since 0.2 has one decimal place, add one decimal place to the answer:7 × 0.2 = 1.4Step 2: Now substitute back.(−2.4) + 1.2 − 1.4Step 3: Go left to right.(−2.4) + 1.2 = −1.2Then −1.2 − 1.4 = −2.6
✅ Answer. −2.6
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