Probability
Birthday Problem
MMTS_Full_Test_18
Grade 12

Question:

The probability that the birthdays of six different persons will fall in exactly two calendar months
$\dfrac{342}{12^5}$
$\dfrac{341}{12^6}$
$\dfrac{341}{12^5}$
$\dfrac{342}{12^6}$

Step-by-Step Solution

Key Concept: Choose 2 months, then distribute 6 birthdays in exactly those 2 months
$P=\frac{\binom{12}{2}(2^6-2)}{12^6}=\frac{66\cdot62}{12^6}=\frac{4092}{12^6}=\frac{341}{12^5}$.
Correct Answer: 3

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