Question:
The following table shows the blood groups of 40 students of a class.
One student of the class is chosen at random. What is the probability that the chosen student's blood group is
(i) O?
(ii) AB?
Solution:
Total number of students = 4
(i) Number of students with blood group O = 14
Let E1 be the event that the selected student's blood group is O.
$\therefore$ Required probability $=P\left(E_{1}\right)=\frac{14}{40}=0.35$
(ii) Number of students with blood group AB = 6
Let E2 be the event that the selected student's blood group is AB.
$\therefore$ Required probability $=P\left(E_{2}\right)=\frac{6}{40}=0.15$