Problem: In a given arithmetic sequence the first term is 2, the last term is 29, and the sum of all the terms is 155. The common difference is:
Answer Choices:
A. 3
B. 2
C. 1927
D. 913
E. 3823
Solution:
s=2n(a+1) where a=2,1=29, and s=155∴155=2n(2+29)=231n,n=10.
But 1=a+(n−1)d; so that 29=2+9d,9d=27,d=3