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1.Set Theory
easy
$20$ teachers of a school either teach mathematics or physics. $12$ of them teach mathematics while $4$ teach both the subjects. Then the number of teachers teaching physics is
A
$12$
B
$8$
C
$16$
D
None of these
Solution
(a) Let $n\,(P)$= Number of teachers in Physics.
$n\,(M)$= Number of teachers in Maths
$n\,(P \cup M) = n(P) + n\,(M) – n\,(P \cap M)$
$20 = n\,(P) + 12 – 4$ ==> $n\,(P) = 12$.
Standard 11
Mathematics
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