Question 1142897
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There are 30 red balls and 20 green balls and some blue balls in a bag. If the probility of finding a red ball is 1/3. 
How many are red balls in the bag 
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            The original formulation is  INCORRECT  and nonsensical,  since the number of red balls is just  GIVEN.


&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;To make sense, &nbsp;the problem &nbsp;MUST &nbsp;BE &nbsp;RE-FORMULATED. &nbsp;For example, &nbsp;in &nbsp;<U>THIS &nbsp;WAY</U> :


<pre>
             There are 30 red balls and 20 green balls and some blue balls in a bag. 

             If the probability of finding a {{{highlight(cross(red))}}} <U>blue</U> ball is 1/3,  how many {{{highlight(cross(red))}}} <U>blue</U> balls are there in the bag ?
</pre>

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;For such formulated problem, &nbsp;the solution is as follows.



<pre>
{{{x/(30 + 20 + x)}}} = {{{1/3}}}  =====>


3x = 30 + 20 + x


2x = 50


x = 50/2 = 25   <U>blue balls</U>.      <U>ANSWER</U>
</pre>