Statistics
NCERT Exemplar Ch 12
CBSE_NCERT_EXEMPLAR_CH12
Grade 10
Question:
If the mean of $x, x+2, x+4, x+6, x+8$ is $11$, find the value of $x$ and the mean of the first 3 observations.
Step-by-Step Solution
Key Concept: Sum $= 5x + 20$. Mean $= \dfrac{5x + 20}{5} = x + 4 = 11 \Rightarrow x = 7$.
Stepwise Solution:
Mean $= x + 4 = 11 \Rightarrow x = 7$. [1.0 Mark]
First 3 observations: $7, 9, 11$. Mean of first 3 $= \dfrac{7 + 9 + 11}{3} = \dfrac{27}{3} = 9$. [1.0 Mark]
Marking Scheme:
• Finding $x = 7$: 1.0 Mark
• Finding mean of first 3 observations $= 9$: 1.0 Mark
Correct Answer:
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