Statistics
RD Sharma
CBSE
Grade 10
Question:
If the mean of the following data is $20.6$, find the value of $p$:
$x$: 10, 15, p, 25, 35
$f$: 3, 10, 25, 7, 5
Step-by-Step Solution
Key Concept: $\sum f = 50$. $\sum f x = 30 + 150 + 25p + 175 + 175 = 530 + 25p$.<br>$\dfrac{530 + 25p}{50} = 20.6 \Rightarrow 530 + 25p = 1030 \Rightarrow 25p = 500 \Rightarrow p = 20$.
$\sum f = 50, \sum f x = 530 + 25p$. [0.5 Mark]
$530 + 25p = 1030 \Rightarrow 25p = 500 \Rightarrow p = 20$. [1.5 Marks]
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🎯 Official CBSE Marking Scheme:
Forming equation $(530 + 25p)/50 = 20.6$: 0.5 Mark
Solving $p = 20$: 1.5 Marks
Correct Answer:
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