Problem:
2(1−21)+3(1−31)+4(1−41)+…+10(1−101)=
Answer Choices:
A. 45
B. 49
C. 50
D. 54
E. 55
Solution:
2(1−21)+3(1−31)+4(1−41)+…+10(1−101)=2(21)+3(32)+4(43)+…+10(109)=1+2+3+…+9=45.
Answer: A.
The problems on this page are the property of the MAA's American Mathematics Competitions