Question:

The value of the expression \(^{47}C_4+ \displaystyle \sum^5_{j = 1} , ^{52-j}C_3\) is

Updated On: Aug 29, 2023
  • $^{47}C_5$
  • $^{52}C_5$
  • $^{52}C_4$
  • None of these
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The Correct Option is C

Solution and Explanation

The correct answer is C:\(^{52}C_4\)
Given expression;
 \(^{47}C_4+ \displaystyle \sum^5_{j = 1} , ^{52-j}C_3\)
\(=  ^{47}C_4+  ^{51}C_3 +  ^{50}C_3 +  ^{49}C_3+  ^{48}C_3 +  ^{47}C_3\)
\(= ( ^{47}C_4+  ^{47}C_3 )+  ^{48}C_3 +  ^{49}C_3+  ^{50}C_3 +  ^{51}C_3\)
\(20mm [using  ^nC_r +  ^nC_{r-1} =  ^{n+1}C_r]\)
\(= ( ^{48}C_4+  ^{48}C_3 )+  ^{49}C_3 +  ^{50}C_3 +  ^{51}C_3\)
\(= ( ^{49}C_4+  ^{49}C_3 )+  ^{50}C_3 +  ^{51}C_3\)
\(= ( ^{50}C_4+  ^{50}C_3 )+  ^{51}C_3\)
\(=  ^{51}C_4+  ^{51}C_3 =  ^{52}C_4\)
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Questions Asked in JEE Advanced exam

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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.