Math Is Fun Forum

juan

Banned

book probability

If each of five people is asked to identify his or her favorite book from a list 10 best-sellers, what is the probability that at least 2 of them identify the same book?

bobbym

bumpkin

From: Bumpkinland

Registered: 2009-04-12

Posts: 109,606

Re: book probability

Hi juan;

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In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

juantheron

Member

Registered: 2011-10-19

Posts: 312

Re: book probability

thanks bobbym i want explanation

would you like to explain it to me

bobbym

bumpkin

From: Bumpkinland

Registered: 2009-04-12

Posts: 109,606

Re: book probability

Hi;

I used a complementary probability. Find the proability of no matches.

If there are 10 best sellers the first person has 10 of them to pick. His probability is 10 / 10. The next person has 9 to pick without matching the first person his probability is 9 / 10. Next person 8 / 10. Continue like that for all five.

Now that you have the probability of no matches 1 minus that must be the probability of 2 or more matches.

---

In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

juan

Banned

Re: book probability

thank bobbym

bobbym

bumpkin

From: Bumpkinland

Registered: 2009-04-12

Posts: 109,606

Re: book probability

Hi jiuan;

Thanks, glad you understand it.

---

In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.