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If 15c3r = 15cr + 3 , Then R is Equal To(A) 5(B) 4(C) 3(D) 2 - Mathematics

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MCQ

If 15C3r = 15Cr + 3 , then r is equal to

Options

  • 5

  •  4

  • 3

  • 2

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Solution

3

\[3r + r + 3 = 15\]  [∵\[{}^n C_x =^n C_y \Rightarrow n = x + y\ \text{or} x = y\]]
\[\Rightarrow 4r + 3 = 15\]
\[ \Rightarrow 4r = 12\]
\[ \Rightarrow r = 3\]
Concept: Combination
  Is there an error in this question or solution?

APPEARS IN

RD Sharma Class 11 Mathematics Textbook
Chapter 17 Combinations
Q 3 | Page 25

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