In a set of first 'x' natural numbers there are 30 prime numbers. Find the number of composite numbers in the above set.

 In a set of first 'x' natural numbers there are 30 prime numbers. Find the number of composite numbers in the above set.
A. x-30
B. 30-x
C. x-29
D. x-31

Ans: D
Explanation:
Number of remaining numbers=x-30
BUT '1' IS NEITHER PRIME NOR COMPOSITE.
Therefore,
No of composite numbers = x-(30+1)=x-31