10th Class Mathematics Probability Question Bank MCQs - Probability

  • question_answer
    A bag contains 8 red balls and some blue balls. If the probability of drawing a blue ball is three times of a red ball, then the number of blue balls in the bag

    A) 12

    B) 18

    C) 24

    D) 36

    Correct Answer: C

    Solution :

    Let there be x blue balls in the bag. \[\therefore \]Total number of balls in the bag \[=\left( \text{ }8\text{ }+\text{ }x \right)\]and Now, \[{{P}_{1}}\]= Probability of drawing a blue ball \[=\frac{x}{8+x}\]and \[{{P}_{2}}\]= Probability of drawing a red ball \[=\frac{8}{8+x}\] It is given that, \[{{P}_{1}}=3{{P}_{2}}\] \[\Rightarrow \,\,\,\,\,\frac{x}{8+x}=3\times \frac{8}{\left( 8+x \right)}\] \[\Rightarrow \,\,\,\frac{x}{8+x}=\frac{24}{8+x}\] Hence, there are 24 blue balls in the bag.


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