Question

Given the Arithmetic sequence A1,A2,A3,A4 61, 74, 87, 100 What is the value of A15?

Answer 1

A15=243
74-61=13
87-61=13
So they're adding 13 every time.
A15 is 11 terms from A4 which is the last one you are given so 11*13=143
143+100=243