A seemingly straightforward maths equation is causing a major stir online, proving that even the simplest problems can be a trap for the unwary.
The puzzle, which has been shared thousands of times, presents a single line of instruction: Divide 40 by half and then add 20. It sounds easy enough, but the results have been wildly divisive.
Many people quickly arrive at an answer of 40, reasoning that half of 40 is 20, and then adding another 20 brings them back to 40. It feels intuitively correct, but according to mathematicians, it's completely wrong.
The Correct Calculation
The critical error lies in the interpretation of the word 'by'. The phrase "divide 40 by half" does not mean to divide 40 into its half (which would be 20). It means to divide 40 by the fraction ½.
In mathematical terms, dividing by a fraction is equivalent to multiplying by its reciprocal. Therefore, dividing 40 by ½ is the same as multiplying 40 by 2.
So, 40 ÷ (½) = 40 x 2 = 80.
The next step is to then add 20.
80 + 20 = 100.
The correct answer to the puzzle "divide 40 by half and add 20" is therefore 100.
Why It's So Confusing
The puzzle is a classic example of a linguistic trick in mathematics. Our brains are wired to process language in a certain way, and the common phrasing "divide by half" is often misheard as "divide in half." This subtle difference changes the entire meaning of the problem.
This viral brain teaser serves as a brilliant reminder that paying close attention to the precise wording is just as important as the calculation itself. So, did you get it right, or were you stumped?
