Statistics
RD Sharma
CBSE
Grade 10
Question:
If the mean of $5$ observations $x, x+2, x+4, x+6, x+8$ is $11$, find the mean of the first three observations.
Step-by-Step Solution
Key Concept: $\text{Mean} = x + 4 = 11 \Rightarrow x = 7$. First 3: $7, 9, 11$. Mean $= 27/3 = 9$.
$x + 4 = 11 \Rightarrow x = 7$. [1.0 Mark]
First three observations: $7, 9, 11 \Rightarrow \text{Mean} = 9$. [1.0 Mark]
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🎯 Official CBSE Marking Scheme:
Finding $x = 7$: 1.0 Mark
Evaluating mean of first 3 observations $= 9$: 1.0 Mark
Correct Answer:
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