On Your Mark, Get Set, Multiply — Quanta Magazine

Did you get caught up in the latest viral math problem, 8÷2(2+2)?

The problem here is simply how we interpret the division symbol. Does ÷ mean divide by the one number right after it or by everything after it? This isn’t much of a concern for most mathematicians, as they don’t use this symbol very often. Ask them to solve this problem and they’ll probably just make the whole thing into a multiplication problem: Once you choose to write it as either

8 \times \frac{1}{2} \times (2 + 2) or 8 \times \frac{1}{2(2+2)},

the ambiguity is gone and the answer is clear. As a multiplication question, this isn’t particularly interesting.

But one multiplication question mathematicians do find interesting may surprise you: What is the best way to multiply?

And what is the best way to multiply? The answer may surprise you! Find out by reading my latest column for Quanta Magazine, freely available here.

09/12/2019 — Happy Permutation Day!

Today we celebrate a Permutation Day! I call days like today permutation days because the digits of the day and the month can be rearranged to form the year.

And not only is it a permutation day, it’s a palindrome day! Thinking of the date as 9/12/19, we can write 91219, which is a palindrome–a number that reads the same backward and forward. Enjoy the day by rearranging something or doing something backwards! Or perhaps even both.

02/19/2019 — Happy Permutation Day!

Today we celebrate a Permutation Day! I call days like today permutation days because the digits of the day and the month can be rearranged to form the year.

We can also consider today a Transposition Day, as we need only a single transposition (an exchange of two numbers) to turn the year into the day and date.

Celebrate Permutation Day by mixing things up! Try doing things in a different order today. Just remember, for some operations, order definitely matters!

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