The arithmetic mean of the data 3, 6, 9, 12, 15 is calculated by adding all the numbers together and then dividing by the total count of numbers.
Arithmetic Mean = (3 + 6 + 9 + 12 + 15) / 5 Arithmetic Mean = 45 / 5 Arithmetic Mean = 9
Therefore, the arithmetic mean of the data 3, 6, 9, 12, 15 is 9.
