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Mathematics

The mean of 18, 24, 15, 2x + 1 and 12 is 21. Find the value of x.

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

⇒ 21 = $\dfrac{18 + 24 + 15 + 2x + 1 + 12}{5}$

⇒ 21 = $\dfrac{70 + 2x}{5}$

⇒ 70 + 2x = 21 x 5

⇒ 70 + 2x = 105

⇒ 2x = 105 - 70

⇒ 2x = 35

⇒ x = $\dfrac{35}{2}$

⇒ x = 17.5

Hence, the value of x is 17.5.

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