The number of letters posted in a certain city on each day for a week is given as follows: 40, 55, 28, 25, 31, 52, 43. Which of the following is not an entry in the three-day moving averages?

37

The correct answer is Option (4) → 37

Given data: 40, 55, 28, 25, 31, 52, 43

Three-day moving averages:

MA₁ = (40 + 55 + 28)/3 = 123/3 = 41

MA₂ = (55 + 28 + 25)/3 = 108/3 = 36

MA₃ = (28 + 25 + 31)/3 = 84/3 = 28

MA₄ = (25 + 31 + 52)/3 = 108/3 = 36

MA₅ = (31 + 52 + 43)/3 = 126/3 = 42

Three-day moving averages: 41, 36, 28, 36, 42

The value that is not in the moving averages: 37