Math Is Fun Forum

mathxyz

Member

From: Brooklyn, NY

Registered: 2024-02-24

Posts: 1,053

Probability of Going Swimmimg

Two guys left their apartments in the same building on a beautiful sunny day. They are off on that particular day. What is the probability that they are both going swimming?

Let me see.

One guy going swimming does not affect what the other guy plans to do on that day. I say these are independent events.

Let A = probability of first guy going swimming.

Let B = probability of second guy going swimming.

P(A and B) = P(A) • P(B)

The probability of the first guy going swimming is yes or no.
The probability for the second guy going swimming is yes or no.

P(A) = 1/2

P(B) = 1/2

P(A and B) = 1/2 • 1/2 = 1/4

You say?

Bob

Administrator

Registered: 2010-06-20

Posts: 10,627

Re: Probability of Going Swimmimg

Yes or no does imply equal probabilities. Will I win the lottery? The answer is yes or no, but definitely not equally likely.  As worded there's no way you can assess the actual probabilities.

Bob

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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

mathxyz

Member

From: Brooklyn, NY

Registered: 2024-02-24

Posts: 1,053

Re: Probability of Going Swimmimg

Yes or no does imply equal probabilities. Will I win the lottery? The answer is yes or no, but definitely not equally likely.  As worded there's no way you can assess the actual probabilities.

Bob

I found this online. It must be a typo. I forgot the online forum where this problem came from. I will also see if there's a free probability textbook I can download. I don't trust online forums. For example, the site algebra.com has tons of typos because students simply don't care about math and thus rush when typing their problems expecting tutors to not only solve their problems but also to correct their typos.