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Question
Find the class boundaries and class marks of the following classes:
55 - 59, 60 - 64, 65 - 69, 70 - 74, 75 - 79, 80 - 84, 85 - 89, 90 - 94 and 95 - 99.
Solution
For the class 55 - 59,
The actual lower limit = 55 - 0.5 = 54.5
The actual upper limit = 59 + 0.5 = 59.5
∴ The class boundaries are 54.5 and 59.5
∴ The class mark = `(1)/(2)(54.5 + 59.5)` = 57
Similarly calculating for the other classes we get the following table:
| Class | Class Boundaries | Class Mark |
| 55 - 59 | 54.5 - 59.5 | 57 |
| 60 - 64 | 59.5 - 64.5 | 62 |
| 65 - 69 | 64.5 - 69.5 | 67 |
| 70 - 74 | 69.5 - 74.5 | 72 |
| 75 - 79 | 74.5 - 79.5 | 77 |
| 80 - 84 | 79.5 - 84.5 | 82 |
| 85 - 89 | 84.5 - 89.5 | 87 |
| 90 - 94 | 89.5 - 94.5 | 92 |
| 95 - 99 | 94.5 - 99.5 | 97 |
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