Mathematics
Consider the following distribution :
| Class | Frequency |
|---|---|
| 0 – 20 | 17 |
| 20 – 40 | 28 |
| 40 – 60 | 32 |
| 60 – 80 | f |
| 80 – 100 | 19 |
If the mean of the above distribution is 50, what is the value of f ?
24
34
56
96
Measures of Central Tendency
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Answer
| Class | Frequency (fi) | Class mark (xi) | fixi |
|---|---|---|---|
| 0 – 20 | 17 | 10 | 170 |
| 20 – 40 | 28 | 30 | 840 |
| 40 – 60 | 32 | 50 | 1600 |
| 60 – 80 | f | 70 | 70f |
| 80 – 100 | 19 | 90 | 1710 |
| Total | ∑ fi = 96 + f | ∑ fixi = 4320 + 70f |
By formula,
Hence, option 1 is the correct option.
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Directions : The marks obtained by 10 students in a class-test were as follows :
36, 64, 48, 52, 57, 73, 26, 39, 78, 67
31. The mean marks of the whole class is :
(a) 49.1
(b) 53.7
(c) 54
(d) 6032. If the maximum marks in the test were 80, the mean percentage of marks obtained by the students is :
(a) 65%
(b) 67.5%
(c) 68%
(d) 72%33. The mean marks of the top 5 scorers in the class is :
(a) 65.4
(b) 66.8
(c) 67.2
(d) 67.834. As per the Board’s instruction each student who obtained less than 50 marks was awarded 3 grace marks. The new mean of the marks thus obtained increases by :
(a) 0.9
(b) 1.2
(c) 1.5
(d) 1.8