Question

The blood groups of 30 students of a class were recorded as under:

Blood Group	A	B	AB	O
No. of students	9	11	4	6

If a student of this class is chosen at random, what is the probability that the chosen student has blood group
(i) O?
(ii) A?
(iii) AB?

Answer 1

Total number of students = 30
(i) Number of students with blood group O = 6

Let E₁ be the event that the selected student has blood group O.

∴ Required probability = P(E₁) = $\frac{6}{30}=\frac{1}{5}$

(ii) Number of students with blood group A = 9

Let E₂ be the event that the selected student has blood group A.

∴ Required probability = P(E₂) = $\frac{9}{30}=\frac{3}{10}$

(iii) Number of students with blood group AB = 4

Let E₃ be the event that the selected student has blood group AB.

∴ Required probability = P(E₃) = $\frac{4}{30}=\frac{2}{15}$

1540 = 38