Problem:
Which of the following is the same as
3−6+9−12+15−18+212−4+6−8+10−12+14​?
Answer Choices:
A. −1
B. −32​
C. 32​
D. 1
E. 314​
Solution:
We have
3−6+9−12+15−18+212−4+6−8+10−12+14​=3(1−2+3−4+5−6+7)2(1−2+3−4+5−6+7)​=32​​
The problems on this page are the property of the MAA's American Mathematics Competitions