Question

Suppose that 20° of boys opted for mathematics and 40% of girls opted for mathematics. What is the probability that a student opted for mathematics if half of the class is girls?​

Answer 1

Answer: 30%

Step-by-step explanation:

Let A be the probability of a student opting for mathematics - it consists of either boy opting for mathematics or girl opting for mathematics. As there is "or" we need to sum these probabilities.

$P(A) = P(B)* P(M|G) + P(G)*P(M|G)$

$P(A) = \frac{1}{2} * \frac{20}{100} + \frac{1}{2} * \frac{40}{100}$

$P(A) = 3/10 = 0.3$

=> 30%