Jump to content
BrainDen.com - Brain Teasers
  • 0

Picking Among Two Pool Balls


BMAD
 Share

Question

A cloth bag contains a pool ball, which is known to be a solid ball. A second pool ball is chosen at random in such a way that it is equally likely to be a solid or a stripe ball. The ball is added to the bag, the bag is shaken, and a ball is drawn at random. This ball proves to be a solid. What is the probability that the ball remaining in the bag is also a solid?
Link to comment
Share on other sites

1 answer to this question

Recommended Posts

  • 0

Two-thirds.

Placing the unknown ball into the bag creates two situations with equal likelihood.
Let O denote a solid ball and I denote a stripe ball. Then your two possibilities are

  1. O O
  2. O I

There are three O's here, equally likely to have been drawn.

Two of them have another O in the same bag.

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...