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In a multiple choice question, there are four alternative answers of which one or more than one is correct. A candidate will get marks on the question only if he ticks the correct answer. The candidate dicides to tick answers at random. If he is allowed up to three chances to answer the question, then find the probability that he will get marks on it.

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The correct Answer is:
A
The total number of ways to answer the equestion
`=""^(4)C_(1)+""^(4)C_(2)+""^(4)C_(3)+""^(4)C_(4)=2^(4)-1=15`
`P("getting marks")=P("correct answer in I chance")+p("correct answer in II chance")+P("correct answer in III chance")`
`=(1)/(15)+((14)/(15).(1)/(14))+((14)/(15).(13)/(14).(1)/(13))=(3)/(15)=(1)/(5)`
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