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  • A bag contains 15 white and some black balls. If the probability of drawing a black ball from the bag is thrice that of drawing a white ball, find the number of black balls in the bag.    </

A bag contains 15 white and some black balls. If the probability of drawing a black ball from the bag is thrice that of drawing a white ball, find the number of black balls in the bag.

 

 

 

 
 
 
 
 

Answers (1)

Given :

\text{White balls}=15

\text{Let black balls}=x

\text{Total balls}=15+x

Probablity that ball is white, 

P_1=\frac{15}{15+x}

Probablity that ball is black, 

P_2=\frac{x}{15+x}

Given , P_2=3P_1

\Rightarrow \frac{x}{15+x}=3\times \frac{15}{15+x}

\Rightarrow x=45

No. of black balls is 45.

Posted by

Ravindra Pindel

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