You Say It’s Your Birthday…

Well, no, actually it’s not my birthday. And it’s not my friend Jacqui’s birthday, either, but she did just celebrate a milestone with us that she wanted to share. Via email, she announced,

I’ve been alive for two billion seconds, a milestone I passed this morning.

This reminded me of a problem from Steve Leinwand’s book, Accessible Mathematics, in which he tells kids his age as a unitless number, then asks them to identify what units he must be using. Along those lines, here are some questions for you.

• How old (in years) is my friend Jacqui?
• What is her date of birth?
• If I tell you that my age is 22,333,444, what units must I be using? Assuming I’m not telling a fib, of course. And what is my age in years and my date of birth?

This reminds me of two math jokes about birthdays.

Statistics show that those who celebrate the most birthdays live longest.

An algebraist remembers that his wife’s birthday is on the (n – 1)^st of the month. Unfortunately, he only remembers this when he is reminded on the n^th.

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