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Question
The percentage of marks obtained by a student in monthly unit tests are given below:
| Unit test: | I | II | III | IV | V |
| Percentage of marks obtained: | 69 | 71 | 73 | 68 | 76 |
Find the probability that the student gets:
(i) more than 70% marks
(ii) less than 70% marks
(iii) a distinction
Solution
The total number of trials is 5.
Remember the empirical or experimental or observed frequency approach to probability.
If n be the total number of trials of an experiment and A is an event associated to it such that A happens in m-trials. Then the empirical probability of happening of event A is denoted by P (A) and is given by
P (A) = `m/n`
(i) Let A be the event of getting more than 70% marks.
The number of times A happens is 3.
Therefore, we have
P (A) = `3/5`
=0.6
(ii) Let B be the event of getting less than 70% marks.
The number of times B happens is 2.
Therefore, we have
P (B) = `2/5`
=0.4
(iii) Let C be the event of getting a distinction.
The number of times C happens is 1.
Therefore, we have
P (C) = `1/5`
= 0.2
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