If average of ten students marks are `47.` If `11th` students marks are also included then average of eleven students marks becomes `45.` Find the marks of `11th` student.

The average marks of 10 students is 30 if 6 marks is added with each students' marks.Then find the new average.

The average marks of 39 students of a class is 50. The marks obtained by 40th student are 39 more than the average marks of all the 40 student are 39 more than the average marks of all the 40 students. Find the mean marks of all the 40 students.

There are 25 boy students and 20 girls students in a school. The average of marks in math of 25 boy students is 52 and the average of marks in math of 20 girl-students is 48. Find the average of marks obtained by the students of the school as a whole.

The average marks of 30 students in a class was 80. After two students left out of the class, the average marks of the remaining students was 82. Then the average marks of the two left out students is