Can You Solve This Math Riddle?

| by John Freund

An Internet debate has erupted over the correct answer to a simple math problem.  

The problem went viral in Japan, where only 60 percent of adults could come up with the right answer, the Daily Mail reports.

The problem reads:  9 - 3 ÷ 1/3 + 1 = ?

The solution lies in a fundamental principle of mathematics that was taught in school, but that most have probably forgotten. The principle's acronym is PEMDAS, which stands for Parenthesis, Exponents, Multiplication/Division, Addition/Subtraction.  

According to, PEMDAS is the order of operations in which you solve a math riddle that has various functions attached to it.  

But there is a caveat to PEMDAS that many have likely forgotten, which is that if functions contain the same precedence, then you solve left to right.  For example, both multiplication and division have the same precedence -- neither comes before the other -- so if they both occur in a math equation, you first solve whichever is most to the left of the equation.  

The same is true for addition and subtraction.  

So, solving equation with PEMDAS in mind, you would divide 3 by 1/3, which -- as you no doubt recall from algebra class -- is the same as multiplying 3 by 3, which gives you 9.  

The equation then reads: 9 - 9 + 1.  

This is where the caveat comes in handy.  Since both addition and subtraction have the same precedence, you perform the subtraction first, since it is on the left hand side of the equation.  

9 - 9 = 0.  

So our new equation reads:  0 + 1, which of course equals 1.  

The final answer is 1.  

Answers have ranged from -1 to 3 to 9, with many falling victim to common mistakes, such as subtracting 3 from 9 first, then dividing by 1/3 and finally adding the 1, or performing the division part first but then skipping to the addition ahead of the subtraction.  

The next time you encounter a math problem like this one, you can impress your friends by remembering the PEMDAS acronym and solving it correctly.

Sources: Daily Mail, Maths Is Fun / Photo credit: YouTube via Daily Mail

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