“How many days old are you?”

“How old are you?” asked young Fred.

(This is not, technically, an ‘Ask Uncle Colin’. It’s an ‘Ask Daddy’.)

“I’m 42, buddy.”

“42 days?”

“No, 42 years!”

“Oh. But how many days is that?”

It is not quite 7:15am on New Year’s Day. I have not yet had my coffee. $42 \times 365$, plus however many leap days, plus however many days there are since my birthday, is not something I am currently capable of calculating.

Whoosh

Like a bad penny.

“It’s $21 \times 730$, and seven 73s are 511, which makes the whole thing 15,330. You’ve had 5 leap years in the 80s and 90s, a futher 5 in the 00s and 10s, and it’s 46 days since your birthday. You’re 15,376 days old.”

You can get that party streamer out of my face, sensei.


Well I didn’t do it that way. I was happy enough to ballpark it.

Obviously, I know how many days there are in a year - but more to the point, I know that in three years, there are about 1,100 days. And 42 years is 14 of those, which makes for 15,400 days - plus a month and a half since my birthday, making 15,445.

If I wanted to be a bit more ninja about it1, I’d note that my 1,100 estimate is a little more than four too many, so I’d need to take about 60 days off of that, making 15,375.

I like to think that even the ninja would give an imperceptible nod at that. Fred, on the other hand, just said “Oh. And how many days old am I?”

Colin

Colin is a Weymouth maths tutor, author of several Maths For Dummies books and A-level maths guides. He started Flying Colours Maths in 2008. He lives with an espresso pot and nothing to prove.

  1. and who doesn’t? []

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I teach in my home in Abbotsbury Road, Weymouth.

It's a 15-minute walk from Weymouth station, and it's on bus routes 3, 8 and X53. On-road parking is available nearby.

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