Question:

If \(\frac{1}{(20-a)(40-a)} + \frac{1}{(40-a)(60-a)} + \ldots + \frac{1}{(180-a)(200-a)} = \frac{1}{256}\), then the maximum value of a is :

Updated On: Sep 20, 2024
  • 198
  • 202
  • 212
  • 218
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The Correct Option is C

Solution and Explanation

\(\frac{1}{20}\left(\frac{1}{20-a} - \frac{1}{40-a} + \frac{1}{40-a} - \frac{1}{60-a} + \ldots + \frac{1}{180-a} - \frac{1}{200-a}\right) = \frac{1}{256}\)

\(⇒\) \(\frac{1}{20}\left(\frac{1}{20-a} - \frac{1}{200-a}\right) = \frac{1}{256}\)

\(⇒\) \(\frac{1}{20} \cdot \frac{180}{(20-a)(200-a)} = \frac{1}{256}\)

\(⇒\) \((20 - a)(200 - a) = 9.256\)

\(⇒\) \(a^2 - 220a + 1696 = 0\)

\(⇒\) \(a = 212, 8\)
Then the maxixum value of \(a = 212\)
So, the correct option is (C): 212

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Concepts Used:

Maxima and Minima

What are Maxima and Minima of a Function?

The extrema of a function are very well known as Maxima and minima. Maxima is the maximum and minima is the minimum value of a function within the given set of ranges.

There are two types of maxima and minima that exist in a function, such as:

  • Local Maxima and Minima
  • Absolute or Global Maxima and Minima