What is the next number in the series - 9 ; 7 ; 7 ; 9 ; 13 ; .....

Answer 1

10(Answer)
3^2 = 9 = 9 (sum of digit)
4^2 = 16 =>1+6= 7 (Sum of digit)
5^2 = 25 = > 2+5=7 (Sum of digit)
6^2 = 36=>3+6 = 9 (Sum of digit)
7^2 = 49 => 9+4 = 13 (Sum of digit)
Similarly
8^2 = 64 =>6+4 = 10 (Sum of digit)

Answer 2

9*7=63=== 6+3=9
7*7=49===4+9=13
7*9=63===6+3=9