The average of 50 numbers is 36. Two of the numbers, 42 and 65, were copied as 24 and 56. What is the correct average?

Explanation

1. 01

   The copied numbers were short by $(42 - 24) + (65 - 56) = 18 + 9 = 27$.

2. 02

   Correct total = $50 \times 36 + 27 = 1{,}827$.

3. 03

   Correct average = $\frac{1827}{50} = 36.54$.