JEE Main 2020 (Online) 7th January Evening ShiftQuestion 1
Let $X=\{n\in N:1\le n\le50\}$. If $A=\{n\in X:n\text{ is a multiple of }2\}$ and $B=\{n\in X:n\text{ is a multiple of }7\}$, then the number of elements in the smallest subset of $X$, containing both $A$ and $B$, is
Sets, Relations and Function
Answer$29$
Solution
The smallest such subset is $A\cup B$; $n(A)=25$, $n(B)=7$, $n(A\cap B)=3$ (multiples of $14$), so $n(A\cup B)=25+7-3=29$.