Problem: The sum of the first eighty positive odd integers subtracted from the sum of the first eighty positive even integers is
Answer Choices:
A. 000
B. 202020
C. 404040
D. 606060
E. 808080 Solution:
Grouping the terms of the difference as (2−1)+(4−3)+⋯+(160−(2-1)+(4-3)+\cdots+(160-(2−1)+(4−3)+⋯+(160− 159)159)159), one obtains 808080 .