Recently I wrote about a math equation that had managed to stir up a debate online. The equation was this one:

8 ÷ 2(2+2) = ?

The issue was that it generated two different answers, 16 or 1, depending on the order in which the mathematical operations were carried out. As youngsters, math students are drilled in a particular convention for the “order of operations,” which dictates the order thus: parentheses, exponents, multiplication and division (to be treated on equal footing, with ties broken by working from left to right), and addition and subtraction (likewise of equal priority, with ties similarly broken). Strict adherence to this elementary PEMDAS convention, I argued, leads to only one answer: 16.

Nonetheless, many readers (including my editor), equally adherent to what they regarded as the standard order of operations, strenuously insisted the right answer was 1. What was going on? After reading through the many comments on the article, I realized most of these respondents were using a different (and more sophisticated) convention than the elementary PEMDAS convention I had described in the article.

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In this more sophisticated convention, which is often used in algebra, implicit multiplication is given higher priority than explicit multiplication or explicit division, in which those operations are written explicitly with symbols like × * / or ÷. Under this more sophisticated convention, the implicit multiplication in 2(2 + 2) is given higher priority than the explicit division in 8÷2(2 + 2). In other words, 2(2+2) should be evaluated first. Doing so yields 8÷2(2 + 2) = 8÷8 = 1. By the same rule, many commenters argued that the expression 8÷2(4) was not synonymous with 8÷2×4, because the parentheses demanded immediate resolution, thus giving 8÷8 = 1 again.

This convention is very reasonable, and I agree that the answer is 1 if we adhere to it. But it is not universally adopted. The calculators built into Google and WolframAlpha use the more elementary convention; they make no distinction between implicit and explicit multiplication when instructed to evaluate simple arithmetic expressions.