Suppose that 5% of men and 0.25% of women have grey hair.
Question:

Suppose that 5% of men and 0.25% of women have grey hair. A haired person is selected at random. What is the probability of this person being male?

Assume that there are equal number of males and females.

Solution:

It is given that 5% of men and 0.25% of women have grey hair.

Therefore, percentage of people with grey hair = (5 + 0.25) % = 5.25%

$\therefore$ Probability that the selected haired person is a male $=\frac{5}{5.25}=\frac{20}{21}$

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