In French, we often talk about BODMAS, but the principle is the same: multiplication and division come before addition and subtraction, even if they appear later in the calculation.
Step-by-step solution
Let’s revisit the expression:
10 − 10 × 10 + 10
We begin with multiplication:
10 × 10 = 100
The expression then becomes:
10 − 100 + 10
Next, we calculate from left to right:
10 − 100 = −90
−90 + 10 = −80
Final result: -80
Why do we make mistakes so often?
Because we tend to read and solve calculations in order, without applying the order of operations. Out of habit or for the sake of speed, mistakes happen quickly. Many people think that all the operations follow each other “as they appear,” when this is not the case.
How to avoid making a mistake?
Here are some practical tips:
Always identify multiplications and divisions first.
Use parentheses if you are unsure. Example: (10 − 10) × (10 + 10) does not give the same result at all.
Read your calculation slowly or aloud.
Practice with other short expressions to automate the reflex.
A little challenge to practice?
Solve this expression:
20 + 5 × 2 − 10
Hint: Multiplication comes before addition and subtraction. The answer is not 40 …
Maths is like a recipe: you just have to follow the order of the steps for the result to be correct.
