Statistics
RD Sharma
CBSE
Grade 10
Question:
If the mean of a frequency distribution is $8.1$ and $\sum f_i x_i = 132 + 5k$, $\sum f_i = 20$, then $k$ is:
(a) $6$
(b) $5$
(c) $4$
(d) $7$
Step-by-Step Solution
Key Concept: $\dfrac{132 + 5k}{20} = 8.1 \Rightarrow 132 + 5k = 162 \Rightarrow 5k = 30 \Rightarrow k = 6$.
132 + 5k = 162 \Rightarrow 5k = 30 \Rightarrow k = 6. [1.0 Mark]
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🎯 Official CBSE Marking Scheme:
Solving $k = 6$: 1.0 Mark
Correct Answer: $6$
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