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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. |
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Answer» 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:
(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. |
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