Carcass wrote:
If \(r = 1 + \frac{1}{3} + \frac{1}{9} + \frac{1}{27}\) and \(s = 1 + \frac{1}{3}r\), then \(s\) exceeds \(r\) by
(A) \(\frac{1}{3}\)
(B) \(\frac{1}{6}\)
(C) \(\frac{1}{9}\)
(D) \(\frac{1}{27}\)
(E) \(\frac{1}{81}\)
Given: \(s = 1 + \frac{1}{3}r\)
Replace \(r\) with \(1 + \frac{1}{3} + \frac{1}{9} + \frac{1}{27}\) to get: \(s = 1 + \frac{1}{3}(1 + \frac{1}{3} + \frac{1}{9} + \frac{1}{27})\)
Expand to get: \(s= 1 + \frac{1}{3} + \frac{1}{9} + \frac{1}{27} + \frac{1}{81}\)
Since we're told \(r = 1 + \frac{1}{3} + \frac{1}{9} + \frac{1}{27}\), we can see that \(s\) exceeds \(r\) by \(\frac{1}{81}\)
Answer: E