Q1. [1]
If the mean of 2, 9, $x+6$, $2x+3$, 5, 10, 5 is 7, then the value of $x$ is:
- A $9$
- B $6$
- C $5$
- D $3$
Previously asked in CBSE board exam
2025 30/3/1 Q15
Generated by claude-sonnet-4-6 · 2026-06-15 10:32 · grounding rag
Model Answer
Option (D) 3
Mean = $\dfrac{2+9+(x+6)+(2x+3)+5+10+5}{7} = 7$
$\Rightarrow 2+9+x+6+2x+3+5+10+5 = 49$
$\Rightarrow 3x + 40 = 49 \Rightarrow 3x = 9 \Rightarrow x = 3$
Explanation
Apply the mean formula: sum of all observations ÷ total number of observations = given mean. Set up the equation, simplify by collecting like terms, and solve for x. There are 7 observations, so multiply mean (7) by 7 to get 49. Watch out for correctly expanding $(x+6)$ and $(2x+3)$ before adding.
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