Logic riddle:

[Fort Fun Indiana]

Well, you know, in recent years there's been a lot of gender confusion.

But an "F" on a math quiz is the same in every language and for every gender.

 

[CrusaderFrank]

Prob(two girls | at least one girl)
= Prob(at least one girl | two girls) * Prob(two girls) / Prob(at least one girl)
= Prob(at least one girl | two girls) * Prob(two girls) / (1 - Prob(no girls))
= 1 * (1/4) / (1 - 1/4)
= 1/3

Or so google says. I never would've guessed it.

maybe they were adopted?

 

[Fort Fun Indiana]

maybe they were adopted?

I like your creative thinking, but that would have no bearing on the answer.

 

[CrusaderFrank]

I like your creative thinking, but that would have no bearing on the answer.

math is hard

 

[Meathead]

But an "F" on a math quiz is the same in every language and for every gender.

OK, so how many genders are there? Used to be a no-brainer when I was younger.

 

[Fort Fun Indiana]

Without using Google, here is is how I arrived at 25%.

The girl could be the older sibling or the younger sibling. Assuming she's the older sibling:

G G (younger sibling is a girl)

G B (younger sibling is a boy)

B G (N/A)

B B (N/A)

That's one in four.

But I could be wrong.

Congrats on the first honest attempt to reason out the answer.

Now, reason through it again, knowing that ALL the possible "B B" permutations have already been eliminated, as you met a female.

 

[Grumblenuts]

Not enough info - she's probably lying because you look so scary.
50% otherwise.

 

[Fort Fun Indiana]

math is hard

Nah, it's pretty darn easy. People make it harder than it is. Just a symbolic language, used to present logic. It is even written in complete sentences.

"x + 6 = 10"

A sentence.

 

[Fort Fun Indiana]

Not enough info - she's probably lying because you look so scary.
50% otherwise.

Show your work, young padawan.

 

[Grumblenuts]

I did, lol.

 

[Fort Fun Indiana]

I did, lol.

Hmm, no. 0% credit.

 

[norwegen]

Congrats on the first honest attempt to reason out the answer.

Now, reason through it again, knowing that ALL the possible "B B" permutations have already been eliminated, as you met a female.

Math is hard.

 

[Fort Fun Indiana]

Math is hard.

The only hard part of this type of mathematics is freeing yourself from preconceptions and mistaken assumptions. Understanding what information you have and don't have, and discerning what you can and cannot correctly infer from it.

 

[Grumblenuts]

Show your work

Introduction to Probability | EquiSeq

equiseq.com

 

[Fort Fun Indiana]

Introduction to Probability | EquiSeq

equiseq.com

So you tried to Google the answer.

Now you fail the entire semester for unethical, dishonest cheating.

Which must really sting, since your answer was wrong anyway.

 

[Grumblenuts]

You didn't even read it.
F.

 

[Fort Fun Indiana]

You didn't even read it.
F.

Don't need to. I could write a better article on probability than that. Those are the fruits of Secondary education.

 

[deannalw]

Math is the debbil

 

[Fort Fun Indiana]

Grumblenuts

Ever take Discrete Mathematics? Having done so would help one arrive at the correct answer.

 

[rightwinger]

A sibling can be either male or female

Probability is 50/50 it is a female

The sex of the other sibling is irrelevant