Question

If $A=\{x:x$ is a prime number between $2$ and $16\},$ then number of subsets of $A$ with exactly two elements is

• A. $5$
• B. $10$
• C. $15$
• D. $20$

Answer 1

The correct option is B $10$

$A=\{3,5,7,11,13\}$
Subsets of $A$ with exactly two elements are $\{3,5\},\{3,7\},\{3,11\},\{3,13\},\{5,7\},\{5,11\},\{5,13\},\{7,11\},\{7,13\},\{11,13\}$
So, there are $10$ subsets with exactly two elements.

Alternate Solution:
Required subsets $={}^5{C}_2=10$