Question

In a certain college 20% of boys and 10% of girls are Studying Mathematics. The girls constitute 40% of the students. If a student is selected and is found to be studying Mathematics find the probability that the student is a boy

Answer 1

Answer:

0.75

Step-by-step explanation:

Let no of girls be x

Let no of boys be y

x = 40% of (x + y)

x/(x+y) = 0.4

y/(x+y) = 1 - x/(x+y) = 0.6

0.2y study maths

0.1x study maths

Probability of a boy selected studying math is

0.2y/(x+y) = 0.2*0.6 = 0.12

Probability of a girl selected studying math is

0.1x/(x+y) = 0.1 * 0.4 = 0.04

Probability of a student studying maths = 0.12 + 0.04 = 0.16

Conditional Probability

P (B/A) = P (A and B) / P (A)

P (Boy selected/ studying math) = P (boy selected studying math) / P (Studying math)

= 0.12 / 0.16 = 0.75