Math Is Fun Forum

phrontister

Real Member

From: The Land of Tomorrow

Registered: 2009-07-12

Posts: 4,876

Special birthday date

Here's a problem that I was inspired to post after seeing evene's question about J.R.R. Tolkien's year of birth, here.

What is the next birthday date on which some people will turn the age that is the last two digits of their year of birth, and that:
(a) has the same day and month as their birthday; and
(b) is the same number of days into the year as their number of birthdays. eg, someone celebrating their 43rd birthday must have their birthday on the 12th of February (ie, 31 Jan days + 12 Feb days = 43).

Last edited by phrontister (2016-09-25 21:48:03)

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"The good news about computers is that they do what you tell them to do. The bad news is that they do what you tell them to do." - Ted Nelson

thickhead

Member

Registered: 2016-04-16

Posts: 1,086

Re: Special birthday date

As today is excluded 27 September 2016(i.e. tomorrow) is the day on which those born on 27 September 2008 will turn 08 years old.This will continue upto 31 December 2016. It will resume on 1 January 2018 for those born in 2009.

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{1}Vasudhaiva Kutumakam.{The whole Universe is a family.}
(2)Yatra naaryasthu poojyanthe Ramanthe tatra Devataha
{Gods rejoice at those places where ladies are respected.}

phrontister

Real Member

From: The Land of Tomorrow

Registered: 2009-07-12

Posts: 4,876

Re: Special birthday date

Hi thickhead;

Thanks for your answer - and excellent thought - but single-digit ages are not exactly what I had in mind. Maybe my wording's a bit loose.

It's probably ok mathematically on occasion, but not really when applied to ages. That's here, down under, in Australia, anyway...but maybe we're a little different from the rest of you.

When their great day arrives, a 07-year-old kid is hardly likely to say to their classmates, "Hey! Guess what! I'm zero-eight today!!" Then they'll have zero-one heck of a job trying to explain to the other single-digit-year-olds in their class what on earth they meant by that! It'd probably take the kid until well after their 05-past-03 home time before any-zero-one would get it!

Please forgive me!

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"The good news about computers is that they do what you tell them to do. The bad news is that they do what you tell them to do." - Ted Nelson

thickhead

Member

Registered: 2016-04-16

Posts: 1,086

Re: Special birthday date

Don't worry. We may be out of seasons but we share same days and nights unlike Americans.
my modified answer is 1958 and the age would be 58.Date and month remain the same.
If the problem could say their age will  share the last 2 digits with the YOB people 108 years old could be accommodated.

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{1}Vasudhaiva Kutumakam.{The whole Universe is a family.}
(2)Yatra naaryasthu poojyanthe Ramanthe tatra Devataha
{Gods rejoice at those places where ladies are respected.}

phrontister

Real Member

From: The Land of Tomorrow

Registered: 2009-07-12

Posts: 4,876

Re: Special birthday date

Hi thickhead;

Sorry...made a huge blunder with the wording! Left an important bit out!

This is a puzzle given to me years ago by someone whose birthday fitted, and I'd forgotten about it until now.

Of course, I've lost the puzzle and repeated it from memory (which is never the best way for me), and only just now did I realise that there was a bit missing.

Fixed now, and should be a little more interesting.

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"The good news about computers is that they do what you tell them to do. The bad news is that they do what you tell them to do." - Ted Nelson

thickhead

Member

Registered: 2016-04-16

Posts: 1,086

Re: Special birthday date

2016 is lost. Next is 28 February 2018.

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{1}Vasudhaiva Kutumakam.{The whole Universe is a family.}
(2)Yatra naaryasthu poojyanthe Ramanthe tatra Devataha
{Gods rejoice at those places where ladies are respected.}

phrontister

Real Member

From: The Land of Tomorrow

Registered: 2009-07-12

Posts: 4,876

Re: Special birthday date

Correct!

It'll never happen to me, though.

...so now you know when my birthday isn't.

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"The good news about computers is that they do what you tell them to do. The bad news is that they do what you tell them to do." - Ted Nelson

thickhead

Member

Registered: 2016-04-16

Posts: 1,086

Re: Special birthday date

Hi phrontister,
29 feb 1960 born will get chance in 2020 and the one on 2 March 1961 in 2022 but what about the one born on 1st march of either year?

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{1}Vasudhaiva Kutumakam.{The whole Universe is a family.}
(2)Yatra naaryasthu poojyanthe Ramanthe tatra Devataha
{Gods rejoice at those places where ladies are respected.}

phrontister

Real Member

From: The Land of Tomorrow

Registered: 2009-07-12

Posts: 4,876

Re: Special birthday date

Hi thickhead;

No, sorry...they both dip out.

The first one was born 1 day too late and the second 1 day too early to meet the 'number of days into the year' constraint.

But them's the breaks!

I drew this up in Excel for a 199-year period, and there is a definite pattern that would be broken if we let these two would-be gatecrashers in!

Last edited by phrontister (2016-09-28 02:36:27)

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"The good news about computers is that they do what you tell them to do. The bad news is that they do what you tell them to do." - Ted Nelson