The total marks for the first ten students are 90 * 10 = <<90*10=900>>900 marks
The 15 students who scored ten marks fewer than the first ten had 90 - 10 = 80 marks each.
The total marks for the following 15 students are 15 * 80 = <<15*80=1200>>1200 marks.
The total number of students who scored above sixty is 10 + 15 = <<10+15=25>>25.
If 50 students were present in the class, those who scored sixty are 50 - 25 = <<50-25=25>>25.
If 25 students scored 60, then their total marks are 60 * 25 = <<60*25=1500>>1500 marks.
The whole class scored a total of 1500 + 1200 + 900 = <<1500+1200+900=3600>>3600 marks.
The average for the class is 3600 / 50 = <<3600/50=72>>72 marks.
#### 72