Question

What is the sum of the last 5 terms of the series 1 9 17... 49?

Answer 1

17,25,33,41,49
the sum of those numbers is 165

Answer 2

The series is increasing by 8 each time.

So that means the complete series is:
1, 9, 17, 25, 33, 41, 49

Add the last 5 digits:
49 + 41 + 33 + 25 + 17 = 165

Answer:
165