Math Is Fun Forum

Fruityloop

Member

Registered: 2009-05-18

Posts: 143

Probability of exhuming a female.

This is from a book.  There are 2 graves.  You know that at least one of the graves contains the body of a woman.  If you randomly select one of the graves and exhume the body, what is the probability that it will be a woman?  The book gives the probability as 3/4.  I thought that the answer in the book was wrong and should be 2/3.  I have come to the conclusion that the book is correct after all and the correct answer is 3/4.

Last edited by Fruityloop (2020-06-14 15:04:56)

renevanderlende

Member

From: The Netherlands

Registered: 2020-01-06

Posts: 39

Re: Probability of exhuming a female.

Purely on intuition: the chance that you'll find a woman is twice the probability you find a man: two graves => might be 2 women. So 2 women and 1 man would yield 2/3 chance you will find a woman. This is because you know that there will at least be a woman in one of the graves. Without that knowledge it would be 50/50.

Shred that book...

Last edited by renevanderlende (2020-03-25 15:40:29)

---

My intro on 'mathisfun forum'...

Bob

Administrator

Registered: 2010-06-20

Posts: 10,626

Re: Probability of exhuming a female.

hi Fruityloop

There's a useful tool that will help here.  It's called a tree diagram.

So don't throw the book yet.  But there's plenty of ways of setting up this problem without exhuming graves.  I think the author needs psychiatric  help.

Bob

---

Children are not defined by school ...........The Fonz
You cannot teach a man anything;  you can only help him find it within himself..........Galileo Galilei
Sometimes I deliberately make mistakes, just to test you!  …………….Bob

renevanderlende

Member

From: The Netherlands

Registered: 2020-01-06

Posts: 39

Re: Probability of exhuming a female.

Wadda ya know, scored myself another F.  Hope you've got glue, Fruityloop....

---

My intro on 'mathisfun forum'...