Quantitative Aptitude
A alone can finish a work in 15 days. A works only for the first two days and last two days. The rest work is done by B and the work is completed in 20 days. In how many days A and B together can finish the work?
\( \frac{90}{8} \)
\( \frac{80}{9} \)
\( \frac{80}{7} \)
\( \frac{70}{8} \)
If \(
\left( x + \frac{1}{x} \right) = 5, \quad \text{and } x > 1,
\) then what is the value of \(
\left( x^8 - \frac{1}{x^8} \right)
\)
60615\(\sqrt{21}\)
60725\(\sqrt{21}\)
60605\(\sqrt{21}\)
60705\(\sqrt{21}\)