The table given below shows the total number of students in five different classes and percentage of number of girls out of total number of students in respective class.
| Classes | Total number of students | Percentage of number of girls out of total number of students |
| 6th | 50 | 42% |
| 7th | 80 | 65% |
| 8th | 75 | 40% |
| 9th | 60 | 60% |
| 10th | 90 | 70% |
Find the sum of the number of boys in 6th, 8th and 10th classes.