Which of the following number will replace the question mark (?) and complete the given number series?
4, 5, 12, 39, 160, ?

Correct option is A

The given series is: 4, 5, 12, 39, 160, ?

The logic alternates between multiplying by a number and adding the same number.

1. 4 → 5: Multiply by 1 and add 1:
   $4\times 1+1=5$

2. 5 → 12: Multiply by 2 and add 2:
   $5\times 2+2=12$

3. 12 → 39: Multiply by 3 and add 3:
   $12\times 3+3=39$

4. 39 → 160: Multiply by 4 and add 4:
   $39\times 4+4=160$

5. 160 → ?: Multiply by 5 and add 5:
   $160\times 5+5=805$

Correct Answer: (a) 805