A teacher wanted to analyse the performance of two sections of students in a mathematics test of 100 marks. Looking at their performances, she found that a few students got under 20 marks and a few got 70 marks or above. So she decided to group them into intervals of varying sizes as follows: 0 - 20, 20 - 30… 60 - 70, 70 - 100. Then she formed the following table:
|
Marks |
Number of student |
|
0 - 20 20 - 30 30 - 40 40 - 50 50 - 60 60 - 70 70 - above |
7 10 10 20 20 15 8 |
|
Total |
90 |
(i) Find the probability that a student obtained less than 20 % in the mathematics test.
(ii) Find the probability that a student obtained marks 60 or above.
Total numbers of students = 90
(i) Numbers of students obtained less than 20% in the mathematics test = 7
Required probability = 7/90
(ii) Numbers of student obtained marks 60 or above = 15+8 = 23
Required probability = 23/90
