Problem:
The sum to infinity of 71+722+731+742+… is:
Answer Choices:
A. 51
B. 241
C. 485
D. 161
E. none of these answers
Solution:
Rearrange the terms:
s1s2s=71+731+⋯=722+742+⋯=s1+s2=1−49171=1−491492=487+482=487=482=489=163
Answer: E.