What will come in place of question mark in the following question?

\(\left( {1 - \frac{1}{2}} \right)\left( {1 - \frac{1}{3}} \right)\left( {1 - \frac{1}{4}} \right)\left( {1 - \frac{1}{5}} \right) \ldots \ldots .\left( {1 - \frac{1}{x}} \right) = ?\)

A (x+1)

B (x -1)

C (1/x)

D x

E None of these

Solution

Correct Answer: Option C

\(\begin{array}{l} \left( {1 - \frac{1}{2}} \right)\left( {1 - \frac{1}{3}} \right)\left( {1 - \frac{1}{4}} \right)\left( {1 - \frac{1}{5}} \right) \ldots \ldots .\left( {1 - \frac{1}{x}} \right) = ?\\ \Rightarrow ? = \left( {1 - \frac{1}{2}} \right)\left( {1 - \frac{1}{3}} \right)\left( {1 - \frac{1}{4}} \right)\left( {1 - \frac{1}{5}} \right) \ldots \ldots .\left( {1 - \frac{1}{{x - 1}}} \right)\left( {1 - \frac{1}{x}} \right)\\ \Rightarrow ? = \frac{1}{2} \times \frac{2}{3} \times \frac{3}{4} \times \ldots \ldots . \times \left( {\frac{{x - 2}}{{x - 1}}} \right)\left( {\frac{{x - 1}}{x}} \right) \end{array}\)

⇒ ? = 1/x

Hence, the required answer is (1/x)

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