9,81,90,810,819,? | series Logical reasoning | WBCS

Complete the series by finding the missing number from the given options.

9,81,90,810,819,?

(a) 7371
(b) 900
(c) 8100
(d) 1638

Correct Answer: a

Solution: 

9*9=81
81+9=90
90*9=810
810+9=819
819*9=7371