What will come in place of the question mark (?) in the following number series? 7, 21, 39, 61, 87, ? MCQ with Answer and Explanation

Explanation:
The differences are: 4, 6, 8, 10. These are increasing by 2. The next difference is 12. Therefore, 30+12=42.

Explanation:
The differences are: 12, 16, 20, 24. These are increasing by 4. The next difference is 28. Therefore, 79+28=107.

Explanation:
The series consists of consecutive prime numbers. The next prime number after 29 is 31? Wait, 31 is prime. But 37 is also prime. Let's check: 11, 17, 23, 29 are primes. The next prime after 29 is 31. So the answer is 31.