Question

Question 27
In a medical examination of students of a class, the following blood groups are recorded.

$\begin{array}{ccccc}\text{Blood group}& A& AB& B& O\\ \text{Number of}& 10& 13& 12& 5\\ \text{students}& & & & \end{array}$

A student is selected at random from the class. The probability that he/she has blood group B is:

A) $\frac{1}{4}$
B) $\frac{13}{40}$
C) $\frac{3}{10}$
D) $\frac{1}{8}$

Answer 1

The answer is C.
Total number of students in a medical examination, n(S) = 40
Number of persons who have B blood group, n(E) = 12
$\therefore$ Probability that he/she has blood group B $=\frac{n\left(E\right)}{n\left(S\right)}=\frac{12}{40}=\frac{3}{10}$