Question

The blood groups of 30 students of class IX are recorded as follows:

$\begin{array}{ccccccccccccccc}& & & & & & & & & & & & & & \\ A,& B,& O,& O,& AB,& O,& A,& O,& B,& A,& O,& B,& A,& O,& O,\\ A,& AB,& O,& A,& A,& O,& O,& AB,& B,& A,& O,& B,& A,& B,& O,\end{array}$

A student is selected at random from the class from blood donation. Find the probability that the blood group of the students chosen is:

(i) A (ii) B (iii) C (iv) O

Answer 1

Total number of students of IX class=30

No . of students of different blood groups

A AB B O

9 3 6 12

(i) Probability of students having blood group A (m)=9

$\therefore$ Probability P(A)=$\frac{m}{n}=\frac{9}{30}=\frac{3}{10}=0.3$

(ii) Probability of students having blood group B (m)=6

$\therefore$ Probability P(A)=$\frac{m}{n}=\frac{6}{30}=\frac{1}{5}=0.2$

(iii) Probability of students having blood group AB(m)3

$\therefore$ Probability P(A)=$\frac{m}{n}=\frac{3}{30}=\frac{1}{10}=0.1$

(iv) Probability of students having blood group O(m)=12

$\therefore$ Probability P(A)=$\frac{m}{n}=\frac{12}{30}=\frac{4}{10}=0.4$