The following is the cumulative frequency distribution (of less than type) of \(1000\) persons each of age \(20\) years and above. Determine the mean age.
| Age below (in years) | Number of persons |
| \(30\) | \(100\) |
| \(40\) | \(220\) |
| \(50\) | \(350\) |
| \(60\) | \(750\) |
| \(70\) | \(950\) |
| \(80\) | \(1000\) |
Answer:
The mean age of \(1000\) persons is .
[Note: Enter the answer in to whole number.]