Mathematics - Probability Question with Solution | TestHub

MathematicsProbabilityConditional probabilityEasy2 minPYQ_2025

MathematicsEasysingle choice

A bag contains 19 unbiased coins and one coin with head on both sides. One coin drawn at random is tossed and head turns up. If the probability that the drawn coin was unbiased, is $\frac{m}{n}, gcd (m, n) = 1$ , then $n^{2} - m^{2}$ is equal to :

Options:

Answer:

Solution:

$Required probability = \frac{\frac{19}{20} \times \frac{1}{2}}{\frac{19}{20} \times \frac{1}{2} + \frac{1}{20} \times 1} = \frac{19}{21} ∴ \frac{m}{n} = \frac{19}{21} \Rightarrow n^{2} - m^{2} = 441 - 361 = 80$

Stream:JEESubject:MathematicsTopic:ProbabilitySubtopic:Conditional probability

⏱ 2mℹ️ Source: PYQ_2025

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