Sometime this week I'll be celebrating my birthday. No... you shouldn’t have... oh... you didn’t... okay! While I’m not big on publicly sharing my birthday, I love the dynamic mathematical subbranch of birthday logic puzzles. So for this week’s Nerd News, here’s one of my favourites.
Your new boss Adam (yes, that’s me!) starts at work.
You and your coworker Chandika ask me, “Hey Adam, when is your birthday?”
I hate a straight answer. But I love brainbusting puzzles.
So I say, “How about this? I’ll give you 10 choices for my birthday, and I’ll whisper you each a hint. I'll tell you only the month of my birthday and Chandika only the number of the day (e.g. 1st, 2nd, 3rd, etc). There's a fat bonus for the first person to tell me my birthday.”
“Okay,” you and Chandika say, “let’s play!”
“Well, I begin, “my birthday is one of the following 10 dates:
Mar 4, Mar 5, Mar 8, Jun 4, Jun 7, Sep 1, Sep 5, Dec 1, Dec 2 or maybe it is Dec 8.”
I then whisper in your ear the month of my birthday, and whisper to Chandika only the number of the day.
Once I’ve shared your hint, you think for a second and blurt out: “I don’t know Adam’s birthday, and I’m certain Chandika doesn’t know it either.”
After hearing what you said, Chandika replies: “Well I didn’t know Adam’s birthday after his hint. But now I know it.”
After hearing what you said, Chandika replies: “Well I didn’t know Adam’s birthday after his hint. But now I know it.”
Once you hear Chandika say this you then say, “Ah - now I know it too."
While your brain is bursting trying to figure out what my birthday is, Bogdan who was walking by, saw the list, heard the rules but not the hints and heard your comments, writes the answer on a piece of paper. Damn you Bogdan!
Tell me the answer that Bodgan wrote and feel free to explain his reasoning by emailing me here. Two randomly selected correct responses will win a signed copy of one of my maths books.
5/2/25 - Here's the solution! Click here
That’s all from me for now. If you'd like more geeky fun, please check out my other newsletters below, or connect with me on LinkedIn and/or X.
Yours in nerdiness,
Adam
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