Logo
Published on

Sum of an AP

Authors
  • avatar
    Name
    Vu Hung
    Twitter

Problem Statement

Find the sum of the first 4040 terms of the arithmetic sequence

9, 13, 17, …9,\ 13,\ 17,\ \ldots

Solutions

Here a=9a=9, d=4d=4, n=40n=40. The 40th term is

l=9+39⋅4=165.l=9+39\cdot 4=165.

So

S40=402(9+165)=20⋅174=3480.S_{40}=\frac{40}{2}(9+165)=20\cdot 174=3480.

Further Readings

Connect with me