A meeting is attended by 750 students. 450 of the students are females. Half the female students are less than thirty years old, and one-fourth of the male students are less than thirty years old. If one of the students of the meeting is selected at random to receive a prize, what is the probability that the person selected is not less than thirty years old?

Question: A meeting is attended by 750 students. 450 of the students are females. Half the female students are less than thirty years old, and one-fourth of the male students are less than thirty years old. If one of the students of the meeting is selected at random to receive a prize, what is the probability that the person selected is not less than thirty years old?

Solution:
A meeting is attended by 750 students. 450 of the students are females.

Half the female students are less than thirty years old
number of females less than thirty years old = 450/2
= 225

male students = 750 - 450
= 300
one-fourth of the male students are less than thirty years old.
number of males less than thirty years old = 300/4
= 75

total number of students less than thirty age = 225 + 75
= 300

the probability that the person selected is less than thirty years old = 300/750
= 2/5

∴ the probability that the person selected is not less than thirty years old = 1 - (2/5)
= (5 - 2)/5
= 3/5