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What is the value of \(\frac{22!-21!}{20!}\)?

Answer and explanation

Correct answer: 441

Since \(22!=22\times21!\), \(22!-21!=21!(22-1)=21\times21!\). Also, \(21!=21\times20!\), so \(\frac{21\times21!}{20!}=21\times21=441\). The value 462 does not follow from the correct factorial simplification. Exam tip: In subtraction involving factorials, first factor out the smaller common factorial.

Related tags

Factorial NotationPermutations And CombinationsFactorial SimplificationAlgebraic SimplificationClass 11 MathematicsMathematicsClass 11 Mcq

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