Question

Mean of 7, 9, 12, x, 4, 11 & 5 is 9. Find the missing observation: (a) 13 (b) 15 (c) 12 (d) None of these

Answer 1

Answer:

(b) 15

Step-by-step explanation:

Given that ;

Mean of 7, 9, 12, x, 4, 11 & 5 is 9.

Sum of observations = 7 + 9 + 12 + x + 4 + 11 + 5

⇒ x + 48

No of observations = 7

We know that ;

Mean = $\sf \dfrac{Sum \: of \: observations}{Number \: of \: observations}$

⇒ 9 = $\sf \dfrac{x + 48}{7}$

⇒ 9 * 7 = x + 48

⇒ 63 = x + 48

⇒ x = 63 - 48

⇒ x = 15

Hence, the value of x is 15.

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Extra information -

What is Mean?

The average of a given set of numbers is called the Arithmetic mean, or simply the mean, of the given numbers.

Mean = $\bf \frac{Sum \: of \: observations }{Number \: of \: observations }$

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Answer 2

Heya!


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We know that ,

$=>mean = \frac{sum \: of \: observations \: }{number \: of \: observations}$

=> Given Observations = 7, 9, 12, x, 4, 11 ,5

=> Sum of observations = 48 + x

→ Number of observations = 7

→ Given Mean = 9

★ Put these values in the formula ,

$= > \frac{48 + x}{7} = 9 \\ \\ = > 48 + x = 63$

•°• x = 63 - 48

→ x = 15

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✔Hence Option (b) 15 is correct !!


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