Mathematics

Find x, if 9, x, 14, 18, x, x, 8, 10 and 4 have a mean of 11.

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Mean = $\dfrac{\text{Sum of all observations }}{\text{Number of all observations}}$

⇒ 11 = $\dfrac{9 + x + 14 + 18 + x + x + 8 + 10 + 4}{9}$

⇒ 11 = $\dfrac{63 + 3x}{9}$

⇒ 11 x 9 = 63 + 3x

⇒ 99 = 63 + 3x

⇒ 3x = 99 - 63

⇒ 3x = 36

⇒ x = $\dfrac{36}{3}$

⇒ x = 12

Hence, the value of x is 12.

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