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10th Class Mathematics Probability Question Bank Probability

  • question_answer
    A bag contains several coloured balls. 28 of them are red. If a ball is drawn at random, the probability of drawing a red ball is\[\frac{4}{9}\].\[x\]balls are added into the box. A ball is then drawn at random. If the probability of drawing a red ball is now\[\frac{1}{2}\],find the value of\[x\].

    A)  4                            

    B)         6

    C)  5                            

    D)         7

    Correct Answer: D

    Solution :

     Let \[n(S)=s,n(R)=28\] \[P(R)=\frac{n(R)}{n(S)}\Rightarrow \frac{4}{9}=\frac{28}{S}\]or \[S=63\] Now, \[\frac{28+x}{63+x}=\frac{1}{2}\]\[\Rightarrow \]\[x=7\]


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