JEE Mains · Maths · STD 12 - 13. probability
A bag contains \((N+1)\) coins \(- N\) fair coins, and one coin with 'Head' on both sides. A coin is selected at random and tossed. If the probability of getting 'Head' is \(\dfrac{9}{16}\), then \(N\) is equal to:
- A \(5\)
- B \(7\)
- C \(8\)
- D \(9\)
Answer & Solution
Correct Answer
(B) \(7\)
Step-by-step Solution
Detailed explanation
Let \(E_1\) be the event of selecting a fair coin and \(E_2\) be the event of selecting the two-headed coin. \(P(E_1) = \dfrac{N}{N+1}\) \(P(E_2) = \dfrac{1}{N+1}\) Let \(H\) be the event of getting a Head. \(P(H|E_1) = \dfrac{1}{2}\) \(P(H|E_2) = 1\) Using the theorem of total…
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