Solution
Given:In this question, we are given that
• The value of the variable E is determined by adding the reciprocals of the first 10 even natural numbers.
To find:We need to determine
• Among the given options, which one can be a possible value of the reciprocal of E.
Approach and Working:As E equals the sum of the reciprocals of the first 10 even natural numbers, we can write E in the following manner:
• E = \(\frac{1}{2}\) + \(\frac{1}{4}\) + \(\frac{1}{6}\) + \(\frac{1}{8}\) + \(\frac{1}{10}\) + \(\frac{1}{12}\) + \(\frac{1}{14}\) + \(\frac{1}{16}\) + \(\frac{1}{18}\) + \(\frac{1}{20}\)
Or, E = \(\frac{1}{2} (1 + \frac{1}{2} + \frac{1}{3} + \frac{1}{4} + \frac{1}{5} + \frac{1}{6} + \frac{1}{7} + \frac{1}{8} + \frac{1}{9} + \frac{1}{10})\)
Now, if we observe the terms within the bracket carefully, we can see that 1 is the largest among all the 10 terms and \(\frac{1}{10}\) is the smallest among all the 10 terms.
• If all 10 terms were equal to \(\frac{1}{10}\), then E would be \(\frac{1}{2} * 10 * \frac{1}{10}\) = \(\frac{1}{2}\).
o But since the actual terms are more, we can say that the value of E is greater than \(\frac{1}{2}\).
• Similarly, if all 10 terms were equal to 1, then E would be \(\frac{1}{2} * 10 * 1 = 5\).
o But since the actual terms are less, we can say that the value of E is less than 5.
Combining the above results, we can say
• \(\frac{1}{2} < E < 5\)
Or, \(2 > \frac{1}{E} > \frac{1}{5}\)
Or, \(2 > \frac{1}{E} > 0.2\)
From the given options, only 0.667 falls in the given range.
Hence, the correct answer is option C.
Answer: CQOW Quant Workshop: