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yuepingzhang
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Joined: April 26th, 2007, 7:49 pm

Number of hair

October 28th, 2007, 2:57 pm

Do you believe that two adults in the world have the same number of hair? What is your reasoning?
 
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Traden4Alpha
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Joined: September 20th, 2002, 8:30 pm

Number of hair

October 28th, 2007, 3:24 pm

Yes. The simplest rationale is that people would have to have at least 6 billion hairs (and be perfectly ordered on the 0 to 6 billion number line) to avoid an overlap. Humans ont have 6 billion hairs, so multiple people must share the same hair count.A variant of the problem is: how small a town would have a high chance that two adults in the town have the same number of hairs? This is a variant of the shared-birthdays-in-a-room problem -- although the chance that a given pair of people in a room share the same birthday is 1/365, the O(n^2) number of possible pairings means the chance of at least one pair sharing a birthday is quite high once the number of people reaches more than a couple dozen. If N is the average number of hairs on the adult human head in that town, I would expect that any population of O(sqrt(N)) adults would have at least one pair with the same number of hairs.
 
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yuepingzhang
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Number of hair

October 28th, 2007, 3:36 pm

Very well, thanks.
 
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Advaita
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Number of hair

October 29th, 2007, 5:14 pm

http://www.pg.com/science/haircare/hair_twh_23.htmon avg, we have only .1m hair. So a whole lot people share same hair numbers by the pigoen-hole principle.Also, 50% of the male population is follicularly challenged by 40 and with a distinct pattern too.So just out of this subset of say 1b males, the average number of folicles is 50,00. And a whole lot of people will have same hair. On the other hand, the female population maybe has range (75000, 200000) i.e. 125,000 distinct types. So sub-setting may give more accurate answers
Last edited by Advaita on October 28th, 2007, 11:00 pm, edited 1 time in total.
 
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xsg
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Number of hair

October 30th, 2007, 3:12 pm

yes, because there are many completely bald ppl with no hairs at all.