Question

In a class, $20$ opted for Physics, $17$ for Maths, $5$ for both and $10$ for other subjects. The class contains how many students?

• A. $35$
• B. $42$
• C. $52$
• D. $60$

Answer 1

Answer: (B)

$42$

$n\left(P\right)=20$

$n\left(M\right)=17$

$n(M\cap P)=5$

$n\left(othersubjects\right)=10$

$n(M\cup P)=n\left(M\right)+n\left(P\right)-n(M\cap P)$

$n(M\cup P)=17+20-5=32$

Total students $=n(P\cup M)+n\left(othersubjects\right)$

$32+10=42$