Question

In a city, 55% of the adults are males. 10% of males use

Answer 1

Using conditional probability:
$P(M|CC) = \frac{P(M and CC)}{P(CC)}$

To find probability that one is both male and uses credit card, you multiply the two probabilities:
$P(M and CC) = 0.55 * 0.1 = 0.055$

To find probability that any person uses a credit card, you add the male and female probabilities:
$P(CC) = P(M and CC) + P(F and CC) \\ \\ P(CC) = 0.055 + (0.45)(0.02) \\ \\ P(CC) = 0.064$

Sub these values into original conditional probability:
$P(M|CC) = \frac{0.055}{0.064} = 0.859$