find the mean marks of a student from the following cumulative frequency distribution
marks number of students
0 and above 80
10 and above 77
20 and above 72
30 and above 65
40 and above 55
50 and above 43
60 and above 28
70 and above 16
80 and above 10
90 and above 8
100 and above 0
Greater than type | Class interval | x | cumulative frequency | frequency(f) | fx |
0 and above | 0-10 | 5 | 80 | 3 | 15 |
10 and above |
10-20 | 15 | 77 | 5 | 75 |
20 and above |
20-30 | 25 | 72 | 7 | 175 |
30 and above | 30-40 | 35 | 65 | 10 | 350 |
40 and above | 40-50 | 45 | 55 | 12 | 540 |
50 and above |
50-60 | 55 | 43 | 15 | 825 |
60 and above | 60-70 | 65 | 28 | 12 | 780 |
70 and above | 70-80 | 75 | 16 | 6 | 450 |
80 and above |
80-90 | 85 | 10 | 2 | 170 |
90 and above |
90-100 | 95 | 8 | 8 | 760 |
100 and above |
100-110 | 105 | 0 | 0 | 0 |
80 | 4140 |