Problem: For a given arithmetic series the sum of the first 50 terms is 200, and the sum of the next 50 terms is 2700. The first term of the series is:
Answer Choices:
A. −1221
B. −21.5
C. −20.5
D. 3
E. 3.5
Solution:
200=250(a+a+49d) and 2700=250((a+50d)+(a+99 d))
Solve these equations simultaneously to obtain a=−20.5.