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TS EAMCET · Maths · Permutation Combination

The least value of the natural number \(n\) satisfying \(C(n, 5)+C(n, 6)>C(n+1,5)\) is

  1. A \(10\)
  2. B \(11\)
  3. C \(12\)
  4. D \(13\)
Verified Solution

Answer & Solution

Correct Answer

(B) \(11\)

Step-by-step Solution

Detailed explanation

\begin{aligned} & \text { We have, }{ }^n C_5+{ }^n C_6>{ }^{n+1} C_5 \\ & { }^{n+1} C_6>{ }^{n+1} C_5 \\ & \Rightarrow \quad \frac{(n+1) !}{6 !(n+1-6) !}>\frac{(n+1) !}{5 !(n+1-5) !} \\ & \Rightarrow \quad 5 !(n-4) !>6 !(n-5) ! \\ & \Rightarrow \quad 5 !(n-4)(n-5) !>6 \cdot 5…