In summary: this is why many people are mistaken on this issue.
This calculation seems very simple at first glance, but it traps a lot of people. The error doesn’t come from the calculation itself, but from a mathematical rule that many have forgotten. And there’s a good chance your brain will fall into the trap too.
At first glance, this calculation seems very simple. You might think you could solve it in a few seconds, without even setting up the problem. And yet, a great many people get the answer wrong. It’s not because they can’t count, far from it. In reality, the error almost always stems from a mathematical rule that many have forgotten over time. And you’ll see that your brain is probably playing a little trick on you.
Why does this calculation trap so many people?
Here is the operation in question:
50 + 50 − 25 × 0 + 2
Most people naturally start calculating from left to right. This makes sense, since that’s how we read. So many people do:
50 + 50 = 100
100 − 25 = 75
75 × 0 = 0
0 + 2 = 2
And they find 2.
Others make a slight variation and find 0.
But these answers are wrong. And it’s not a question of intelligence, it’s simply a natural reflex: our brain likes to go in order, without thinking about mathematical rules.
The rule that many have forgotten
In mathematics, there is a specific order for performing operations. This rule is learned in school, but many people forget it over the years.
The rule is simple:
Multiplication and division first,
then addition and subtraction
This rule is often called: « multiplication before addition ».
This means that in our calculation, we should not start with 50 + 50.
We must first do 25 × 0.
Let’s do the calculation again correctly
We repeat the operation, respecting the rule:
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