Final answer:
The fourth number is 11, calculated by subtracting the sum of the first three numbers from the total sum required for a mean of 10.
Step-by-step explanation:
The correct answer is that the fourth number is 11. To find the fourth number when the mean of four numbers is 10, we can use the formula for the mean: (sum of all numbers) / (number of numbers).
We know that the first three numbers are 12, 6, and 11, which add up to 29. Since the mean of the four numbers is 10, their total sum must be 10 x 4 = 40. Therefore, to find the fourth number, we subtract the sum of the first three numbers from the total sum: 40 - 29 = 11.
To find the fourth number, we need to calculate the sum of the four numbers and subtract it from the mean multiplied by the number of observations. The sum of the first three numbers (12, 6, 11) is 29. The mean is 10 and there are 4 numbers in total. So, the sum of all four numbers will be (10 x 4) - 29 = 11. Therefore, the fourth number is 11.