Cheryl’s Birthday Problem and Information Filtering

I love seeing teasers about math and logic gain popular appeal! Here’s the math (specifically, logic) problem that the internet is talking about today:

Cheryl's birthday problem

You can get the full problem nicely presented on either The Guardian or The New York Times websites. A number of other sites are talking about it today, too. Just Google “Cheryl birthday problem.”

I spent some time with the problem and put together this response here. I know that various online outlets have discussed the answer as well; here are the respective solutions presented by The Guardian and The New York Times (don’t click those links until you think about the problem for yourself). But I think there’s a useful “information” framework to use in considering how to arrive at the answer. I discuss that framework at the end.

Spoiler alert — I’m going to discuss the birthday answer starting in the next paragraph.

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Meet Zequals, a mental math tool

Can some simple rounding help us be more accurate and confident with mental math? The man behind this symbol proposes just that: And it turns out it’s fairly accurate: Basically, using some simplification of numbers we can do mental multiplication more accurately (generally). Confused by the squiggles and colors? Don’t be intimidated. Read more: Zequals: the new symbol that will make us all better at sums | … Continue reading Meet Zequals, a mental math tool

What is a “math person” anyway?

I’m struck by how many people will readily disavow their math skills with a single statement of “I’m not a math person.” You’ve heard it many times from friends, or perhaps from yourself. Maybe you’ve excused your way out of situations requiring calculation, geometrical thinking, or ratios. “I’m not a math person” seems like a fine excuse. But what if in a social situation you … Continue reading What is a “math person” anyway?

RIP Mandelbrot, Father of Fractals

“Mandelbrot set” may sound like complicated math. But many of us already recognize these sets as “fractals” — a term that Dr. Mandelbrot coined. I remember reading about the Mandelbrot set in college. I didn’t realize at the time that Mandelbrot was still alive. Then as I read the New York Times today I came across his obituary. Turns out he passed away last week. … Continue reading RIP Mandelbrot, Father of Fractals