Question

If the arithmetic mean of 5, 7, 9, x is 9 then the value of x is (A) 11

Answer 1

5+7+9+X/4=9
5+7+9+X=9*4
21+X=36
X=36-21
X=15

Answer 2

The value of x is equal to 15.

Step-by-step explanation:

Given,

The arithmetic mean = 9

To find, the value of x = ?

We know that,

Arithmetic mean =$\dfrac{Sum of observations}{Number of observations}$

⇒ $\dfrac{5+7+9+x}{4}=9$

⇒ $\dfrac{21+x}{4}=9$

⇒ $21+x=9\times 4=36$

⇒ $x=36-21=15$

∴ $x=36-21=15$

Hence, the value of x is equal to 15.