A family has two boys and two girls, one of whom is called Jane. Two of them are chosen at random
a. Find the probability that they are both girls, given that one of them is a girl.
b. Find the probability that they are both girls, given that one of them is Jane.

Question

A family has two boys and two girls, one of whom is called Jane. Two of them are chosen at random
a. Find the probability that they are both girls, given that one of them is a girl.
b. Find the probability that they are both girls, given that one of them is Jane.

anonymous · Answer

This doesn't make any sense

deoxna · Answer

Thats IB HL Math of course it doesn't make sense

anonymous · Answer

From the "given" statement, list all your possibilities. Then count the possibilities that are "good."

anonymous · Answer

a. Find the probability that they are both girls, given that one of them is a girl.
b. Find the probability that they are both girls, given that one of them is Jane.

It might help if we give them all names.
Jane and Jill are ladies. Bill and Bob are fellas.

Given that one of them is a girl gives us these possibilities:
Jane& Bill, Jane & Bob, Jill& Bill, Jill & Bob, Jill & Jane

deoxna · Answer

So the only posibilty that both are girls is 1/5. Genius @SmoothMath 

So then, using the same logic, the possibilities picking a girl given that Jane has already been chosen is: Jane & Jill, Jane & Bob, Jane & Bill, so it is a possibility of 1/3.

Thanks!

However my teacher wants us to do this using tree diagrams for future, more ambigious, problems. How could a tree diagram be made of this situation?

deoxna · Answer

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