Question 75 of 480
If the mean of the numbers 0, (x+2), (3x+6), and (4x+8) is 4, find their mean deviation.
Correct Answer:
C
Explanation
To solve the problem, we need to follow a series of steps to find the mean deviation of the numbers given. Let's break it down step-by-step.
### Step 1: Calculate the Mean
We are given four numbers:
1. \(0\)
2. \(x + 2\)
3. \(3x + 6\)
4. \(4x + 8\)
To find the mean of these numbers, we first need to sum them up and then divide by the number of values (which is 4).
**Sum of the numbers:**
\[
0 + (x + 2) + (3x + 6) + (4x + 8) = 0 + x + 2 + 3x + 6 + 4x + 8
\]
Combining like terms:
\[
(0 + x + 3x + 4x) + (2 + 6 + 8) = 8x + 16
\]
**Mean:**
\[
\text{Mean} = \frac{\text{Sum of the numbers}}{\text{Number of values}} = \frac{8x + 16}{4} = 2x + 4
\]
We are told that this mean equals 4:
\[
2x + 4 = 4
\]
**Solving for \(x\):**
\[
2x = 4 - 4
\]
\[
2x = 0 \implies x = 0
\]
### Step 2: Substitute \(x\) Back into the Numbers
Now that we have \(x = 0\), we can substitute it back into the original numbers:
1. \(0\)
2. \(x + 2 = 0 + 2 = 2\)
3. \(3x + 6 = 3(0) + 6 = 6\)
4. \(4x + 8 = 4(0) + 8 = 8\)
So the numbers are now:
- \(0\)
- \(2\)
- \(6\)
- \(8\)
### Step 3: Calculate the Mean Deviation
**Mean Deviation** is defined as the average of the absolute differences between each number and the mean of the numbers.
**Step 3.1: Calculate the Mean of the New Numbers**
\[
\text{Mean} = \frac{0 + 2 + 6 + 8}{4} = \frac{16}{4} = 4
\]
**Step 3.2: Calculate the Absolute Deviations**
Now we find the absolute deviations from the mean (which is 4):
1. \(|0 - 4| = 4\)
2. \(|2 - 4| = 2\)
3. \(|6 - 4| = 2\)
4. \(|8 - 4| = 4\)
**Step 3.3: Sum of Absolute Deviations**
\[
\text{Sum of absolute deviations} = 4 + 2 + 2 + 4 = 12
\]
**Step 3.4: Mean Deviation**
\[
\text{Mean Deviation} = \frac{\text{Sum of absolute deviations}}{\text{Number of values}} = \frac{12}{4} = 3
\]
### Conclusion
The mean deviation of the numbers is **3**.
### Explanation of Options
- **Option A (0)**: This is incorrect because the mean deviation cannot be zero unless all numbers are the same, which is not the case here.
- **Option B (2)**: This is incorrect as the calculated mean deviation is higher than 2.
- **Option C (3)**: This is the correct answer, as we calculated the mean deviation to be 3.
- **Option D (4)**: This is incorrect because the mean deviation is not equal to the mean itself, and we calculated it to be 3.
### Revision Summary
- The mean of the numbers was calculated to be 4, leading to \(x = 0\).
- The new numbers were determined to be \(0, 2, 6, 8\).
- The mean deviation was calculated as 3 by finding the absolute deviations from the mean.
- The correct answer is **C (3)**.