Mark's 47... You 37, (18 years = 71 and 61) 6 years ago, 41 and 31... Happy birthday...

Hi All,

So much fun to read your column :).

Happy Birthday !!!!!!

John

It's close, but I don't think it's enough information without further knowledge. Here's what the data you supplied gives (using ipython because doing it by hand would be too tedious):

In [1]: import numpy as np

In [2]: primes = np.array([2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47, 53, 59, 61, 67, 71, 73, 79, 83, 89, 97])

In [3]: set(primes-6) & set(primes+6) & set(primes+18) & set(primes)
Out[3]: {23, 37, 47}

So the correct ages are in there.

If you were to add e.g. that there's 10 years between you, only one answer would remain;

In [4]: set(primes-6) & set(primes+6) & set(primes+18) & set(primes) & set(primes-10)
Out[4]: {37}

Deb -- Sorry to inflame your allergy!

Roland --- I love your mathematical analysis! Of course, the human reader would look at the header ("homesteading year 10") and realize that we can delete all numbers less than 28 assuming we began homesteading in adulthood. On the other hand, they might not be able to tell who is older --- me or Mark --- which would still leave two numbers in the possible solution set. So, you're right --- I need to add more data to my word problem next time around!