COMEDK · Maths · 4. Permutation Combination
If \(\left[{ }^{n+1} C_{r+1}\right]:\left[{ }^n C_r\right]:\left[{ }^{n-1} C_{r-1}\right]=11: 6: 3\) then \(n r=\)
- A 20
- B 30
- C 50
- D 40
Answer & Solution
Correct Answer
(C) 50
Step-by-step Solution
Detailed explanation
Given the ratio \(^{n+1}C_{r+1} : ^{n}C_{r} : ^{n-1}C_{r-1} = 11 : 6 : 3\). First, consider the ratio \(\dfrac{^{n+1}C_{r+1}}{^{n}C_{r}} = \dfrac{11}{6}\). Using the formula \(^{n}C_{r} = \dfrac{n!}{r!(n-r)!}\), we have…
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