The average of marks of 28 students in Mathematics was 50; 8 students left the school, then this average increased by 5. What is the average of marks obtained by the students who left the school ?

The average of marks of 28 students in Mathematics = 50 Total marks of 28 students = 28 × 50 = 1400 When 8 students left , The average of marks of 20 students = 55 Total marks of 20 students = 20 × 55 = 1100 ∴ Total marks of 8 students = 1400 – 1100 = 300 ∴ Average = 300 ÷ 8 = 37.5