Jump to content
BrainDen.com - Brain Teasers
  • 0

Born on a Wednesday


rocdocmac
 Share

Question

The probability that any one person selected at random was born on a Wednesday, is 0.1429 (~14 %).

 

What is the probability that of any …

(1)   Seven persons chosen at random, exactly one was born on a Friday?

(2)   Five persons chosen at random, three were born on a Sunday?

 

[Mr Moderator, if this question has appeared before, please remove it!]

 

 

 

 

Edited by rocdocmac
Changed font
Link to comment
Share on other sites

12 answers to this question

Recommended Posts

  • 0
2 hours ago, rocdocmac said:

@Molly Mae

  Hide contents

You're on the right track, but something is missing from both answers!

 

I'm hoping it's something from a probability perspective.  I assume an equal likelihood of being born on any day of the week.  I don't know if I need to state that assumption.

As I mentioned before, I'm not terribly great at this.

Is it perhaps that I calculated for (1) the probability that a specific person was born on a Friday?  If that's the case, perhaps (1) should be 0.39656906002.  But 40% seems a bit high.  It makes sense in my head logically, but the answer just seems a bit too high.  You can see that I'm a bit out of my element.  =P

Link to comment
Share on other sites

  • 0
27 minutes ago, Molly Mae said:

I'm hoping it's something from a probability perspective.  I assume an equal likelihood of being born on any day of the week.  I don't know if I need to state that assumption.

As I mentioned before, I'm not terribly great at this.

 

  Reveal hidden contents

Is it perhaps that I calculated for (1) the probability that a specific person was born on a Friday?  If that's the case, perhaps (1) should be 0.39656906002.  But 40% seems a bit high.  It makes sense in my head logically, but the answer just seems a bit too high.  You can see that I'm a bit out of my element.  =P

 

Yeah, I'm pretty sure the above can't be right.

 

Perhaps 0.33518439994 is closer to the answer.

EDIT: But that still seems pretty high, in my mind.

Edited by Molly Mae
Link to comment
Share on other sites

  • 1

Let's see if I remember some probability. 

I assume a 14% chance of being born on any given day of the week. 

1) The probability that exactly one person out of seven is born on a Friday is 7 * (.14) * .86^6 = 39.6%. 

2) The probability that three out of five people are born on a Sunday is (5 choose 3) * .14^3 * .86^2 = 2%. 

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Answer this question...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

Loading...
 Share

  • Recently Browsing   0 members

    • No registered users viewing this page.
×
×
  • Create New...