Question

if 15 is the fifth number in a series of five consecutive odd numbers, what is the third number in the series ?

Answer 1

The five numbers can be represented by (2n+1), (2n+3), (2n+5), (2n+7), and (2n+9), where n is an integer. 
2n+9 = 15 
n = 3 

The third number is 2n+5 = 11