Question 1186382
.
A jar contains 4 red marbles, numbered 1 to 4, and 11 blue marbles numbered 1 to 11.
a) A marble is chosen at random. If you're told the marble is blue, what is the probability that it has the number 2 on it?

b) The first marble is replaced, and another marble is chosen at random. 
If you're told the marble has the number 1 on it, what is the probability the marble is blue?
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            It is a conditional probability problem.



<pre>
(a)  There are 11 blue marbles.

     The probability that the selected blue marble has the number 2 is  {{{1/11}}}.    <U>ANSWER</U>


     To solve such problems, we reduce the total space of events (4+11 = 15 marbles)

     to its smaller sub-space, consisting of 11 blue marbles.



(b)  There are 2 marbles with the number 1 on them.    They are red and blue.

     The probability that the selected marble, marked 1, is blue is  {{{1/2}}}.        <U>ANSWER</U>


     To solve such problems, we reduce the total space of events (4+11 = 15 marbles)

     to its smaller sub-space, consisting of 2 marbles, market by number 1.
</pre>

Solved.


As I said, the method to solve these two problems is the same.


Therefore, I explain the solutions practically in the same words.


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On conditional probability, &nbsp;see the lessons

&nbsp;&nbsp;&nbsp;&nbsp;- <A HREF=https://www.algebra.com/algebra/homework/Probability-and-statistics/Conditional-probability-problems.lesson>Conditional probability problems</A> 

&nbsp;&nbsp;&nbsp;&nbsp;- <A HREF=https://www.algebra.com/algebra/homework/Probability-and-statistics/More-conditional-probability-problems.lesson>Conditional probability problems REVISITED</A> 

&nbsp;&nbsp;&nbsp;&nbsp;- <A HREF=https://www.algebra.com/algebra/homework/Probability-and-statistics/More-problems-on-Conditional-probability.lesson>More problems on Conditional probability</A> 

in this site.


Read them to develop your skills and knowledge.


Also, &nbsp;you have this free of charge online textbook in ALGEBRA-II in this site

&nbsp;&nbsp;&nbsp;&nbsp;- <A HREF=https://www.algebra.com/algebra/homework/complex/ALGEBRA-II-YOUR-ONLINE-TEXTBOOK.lesson>ALGEBRA-II - YOUR ONLINE TEXTBOOK</A>.


The referred lessons are the part of this online textbook under the topic &nbsp;"<U>Solved problems on Probability</U>" 
and &nbsp;"<U>Additional problems on Probability</U>". 



Save the link to this textbook together with its description


Free of charge online textbook in ALGEBRA-II
https://www.algebra.com/algebra/homework/complex/ALGEBRA-II-YOUR-ONLINE-TEXTBOOK.lesson


into your archive and use when it is needed.