Question

The below frequency distribution table represents the blood group of 30 students of a class. Use this table to determine the probability that a student of this class selected at random, has blood group AB.

Blood Group	Number of students
A	9
B	6
AB	3
O	12
Total	30

Answer 1

Hint: Probability of an event is defined as the Number of favourable outcomes divided by the total sample space. Identify the number of favourable outcomes and total sample space for the event according to the question. Use the formula of the probability to obtain the result.

Complete step-by-step answer:
Probability of an event is defined as the chance of that event taking place. Mathematically probability of an event is defined as the number of favourable outcomes divided by the total sample space.
Sample space for an event is defined as the total amount of possible outcomes from which an event is likely to happen. The sample space contains the favourable and unfavourable events. Here the favourable event for which the probability has to be calculated is for a student picked having blood group as AB. The total number of students in the class represents the total sample space as any one of the students can be picked. The probability of a student picked and having blood group AB will be Number of students having Blood group AB divided by the total number of students.
From the frequency distribution we can observe that the number of students having blood group AB are 3, and the total number of students are 30.
Therefore the probability of a student having blood group AB is $\dfrac{3}{{30}}$.
$
 \Rightarrow P = \dfrac{1}{{10}} \\
   = 0.1 \\
$
Thus, probability for a student picked having blood group AB is 0.1.

Note: Probability of an event is the chance of that event taking place. The concept of identifying the number of favourable outcomes and the total sample space is important to find the probability of an event. The probability of any event always lies between 0 and 1.