The average of a set of ten numbers is 40. If a number is removed from the set, then the average of the remaining numbers becomes 38. What was the number that was removed?

42 54 60 58

58

Sum of 10 numbers = 10 × 40 = 400 Sum of 9 numbers = 9 × 38 = 342 Removed number is = 400 - 342 = 58