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Evaluate: $$\frac{1}{{15}} + \frac{1}{{35}} + \frac{1}{{63}} + \frac{1}{{99}} + \frac{1}{{143}}$$
Answer & Solution
Correct Answer:
Option
B
$$\eqalign{
& \frac{1}{{15}} + \frac{1}{{35}} + \frac{1}{{63}} + \frac{1}{{99}} + \frac{1}{{143}} \cr
& = \frac{1}{2}\left[ {\frac{1}{3} - \frac{1}{5} + \frac{1}{5} - \frac{1}{7}\,.\,.\,.\,.\,.\,\frac{1}{{11}} - \frac{1}{{13}}} \right] \cr
& = \frac{1}{2}\left[ {\frac{1}{3} - \frac{1}{{13}}} \right] \cr
& = \frac{1}{2} \times \frac{{10}}{{39}} \cr
& = \frac{5}{{39}} \cr} $$
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