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14.Probability
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Probability that a student will succeed in $IIT$ entrance test is $0.2$ and that he will succeed in Roorkee entrance test is $0.5$. If the probability that he will be successful at both the places is $0.3$, then the probability that he does not succeed at both the places is
A
$0.4$
B
$0.3$
C
$0.2$
D
$0.6$
Solution
(d) Let $A$ denotes the event that the student is selected in $IIT$ entrance test and $B$ denotes the event that he is selected in Roorkee entrance test. Then
$P(A) = 0.2,\,\,P(B) = 0.5$ and $P(A \cap B) = 0.3.$
Required probability $ = P(\overline A \cap \overline B) = 1 – P(A \cup B)$
$ = 1 – (P(A) + P(B) – P(A \cap B))$
$ = 1 – (0.2 + 0.5 – 0.3) = 0.6$.
Standard 11
Mathematics
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