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A letter is known to have come either from LONDON or CLIFTON. On the envelop just two consecutive letter 'ON' are visible. The probability that the letter has come from LONDON is:

Solution

✅ Correct Option: 2

LONDON has 55 consecutive letter pairs of which 22 are ON; CLIFTON has 66 pairs of which 11 is ON. By Bayes' theorem the probability is 12⋅2512⋅25+12⋅16=1217\frac{\frac{1}{2}\cdot\frac{2}{5}}{\frac{1}{2}\cdot\frac{2}{5}+\frac{1}{2}\cdot\frac{1}{6}} = \frac{12}{17}.

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