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COMEDK · Maths · 36. Probability

Samhita faces a three-headed dragon. She wins a 'Tactical medal' if she manages to defeat exactly one of the three heads.
The battle proceeds head-by-head under the following conditions:
The probability of defeating the first head is \(\dfrac{1}{3}\).
After a win: if she defeats a head, the probability of defeating the next head is \(\dfrac{2}{3}\).
After a loss: if she fails to defeat a head, the probability of defeating the next head is \(\dfrac{1}{4}\).
What is the probability that Samhita earns the 'Tactical medal'?

  1. A \(\dfrac{5}{36}\)
  2. B \(\dfrac{23}{72}\)
  3. C \(\dfrac{19}{72}\)
  4. D \(\dfrac{17}{72}\)
Verified Solution

Answer & Solution

Correct Answer

(C) \(\dfrac{19}{72}\)

Step-by-step Solution

Detailed explanation

Let \(W\) denote defeating a head (win) and \(L\) denote failing to defeat a head (loss). The probability of exactly one win in three battles is the sum of the probabilities of the sequences \(WLL\), \(LWL\), and \(LLW\). From the given conditions, the initial probabilities are:…