Question:

If \(\frac{1}{6!}+\frac{1}{7!}=\frac{x}{8!}\), find x.

Updated On: Oct 21, 2023
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Solution and Explanation

Given, \(\frac{1}{6!}+\frac{1}{7!}=\frac{x}{8!}\)

\(⇒\frac{1}{6!}+\frac{1}{7\times6!}=\frac{x}{8\times7\times6!}\)

\(⇒\frac{1}{6!}(1+\frac{1}{7})=\frac{x}{8\times7\times6!}\)

\(⇒1+\frac{1}{7}=\frac{x}{8\times7}\)

\(⇒\frac{8}{7}=\frac{x}{8\times7}\)

\(⇒x=\frac{8\times8\times7}{7}\)

\(∴x=64\)

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Concepts Used:

Permutations and Combinations

Permutation:

Permutation is the method or the act of arranging members of a set into an order or a sequence. 

  • In the process of rearranging the numbers, subsets of sets are created to determine all possible arrangement sequences of a single data point. 
  • A permutation is used in many events of daily life. It is used for a list of data where the data order matters.

Combination:

Combination is the method of forming subsets by selecting data from a larger set in a way that the selection order does not matter.

  • Combination refers to the combination of about n things taken k at a time without any repetition.
  • The combination is used for a group of data where the order of data does not matter.