The average of 20 observations was calculated as 45. It was later found that the value 36 had been wrongly read as 63. What is the correct average?

Explanation

1. 01

   Wrong total = $20 \times 45 = 900$.

2. 02

   Correct total = $900 - 63 + 36 = 873$.

3. 03

   Correct average = $\frac{873}{20} = 43.65$.