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JEE Main & Advanced Sample Paper JEE Main - Mock Test - 1

  • question_answer
    A purse contains 4 copper and 3 silver coins, and a second purse contains 6 copper and 2 silver coins. A coin is taken out from any purse, the probability that it is a copper coin is

    A) 3/7                  

    B) 4/7                

    C) 3/4                  

    D) 37/56       

    Correct Answer: D

    Solution :

    [d]: Let \[{{E}_{1}}=\] Event of choosing purse I \[{{E}_{2}}=\] Event of choosing purse II A = Event that the coin drawn is of copper. \[\therefore \]\[P({{E}_{1}})=\frac{1}{2}=P({{E}_{2}})\] \[\therefore \]\[P(A/{{E}_{1}})=\frac{4}{7},P(A/{{E}_{2}})=\frac{3}{4}\] By theorem of total probability, \[P(A)=P({{E}_{1}})P(A/{{E}_{1}})+P({{E}_{2}})P(A/{{E}_{2}})\] \[=\frac{1}{2}\times \frac{4}{7}+\frac{1}{2}\times \frac{3}{4}=\frac{37}{56}\]     


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