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JEE Mains · Maths · STD 11 - 14. probability

Two dice are thrown  \(5\) times, and each time the sum of the numbers obtained being  \(5\) is considered a success. If the probability of having at least \(4\) successes is \(\frac{\mathrm{k}}{3^{11}}\), then \(\mathrm{k}\) is equal to

  1. A \(82\)
  2. B \(123\)
  3. C \(164\)
  4. D \(75\)
Verified Solution

Answer & Solution

Correct Answer

(B) \(123\)

Step-by-step Solution

Detailed explanation

Probability of success \(=\frac{1}{9}=p\) Probability of failure \(q =\frac{8}{9}\) \(P (\text { at least } 4 \text { success })= P (4 \text { success })+ P (5 \text { success })\) \(={ }^5 C _4 p ^4 q +{ }^5 C _5 p ^5=\frac{41}{3^{10}}=\frac{123}{3^{11}}\) \(k =123\)
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