Question
Calculate the mean of the distribution given below using the short cut method.
| Marks | 11 - 20 | 21 - 30 | 31 - 40 | 41 - 50 | 51 - 60 | 61 - 70 | 71 - 80 |
| No. of students | 2 | 6 | 10 | 12 | 9 | 7 | 4 |
