The average mark of 40 students in a test was found to be 72. Later it was discovered that one student's mark had been entered as 48 instead of 84. What is the correct average?

Explanation

1. 01

   The entered total was 36 too low $(84 - 48)$.

2. 02

   Correct total = $40 \times 72 + 36 = 2{,}916$.

3. 03

   Correct average = $\frac{2916}{40} = 72.9$.