# Thread: following numbers have a mean of 5, find the value of x

1. ## following numbers have a mean of 5, find the value of x

Hi I need your help. I can't work out how to find X. I know how to find the cofficient of the variation if I knew what X was.

Thanks
If the following numbers have a mean of 5, find the value of x and find the coefficient of variation

5 x 2 x 9 11 1

2. ## Re: following numbers have a mean of 5, find the value of x

write down the formula for the mean:

$\displaystyle mean = 5 = \frac{5+x+2+x+9+11+1}{7}$
$\displaystyle 5 = \frac{2x + 28}{7}$
$\displaystyle 5 = \frac{2x}{7} + \frac{28}{7}$
solve for x

Once you have x, you can compue the coefficient of variation manually.

3. ## Re: following numbers have a mean of 5, find the value of x

$\displaystyle \frac{5+x+2+x+9+11+1}{7} = 5$

then

$\displaystyle \frac{2x+5+2+9+11+1}{7} = 5$

Can you find it now?

4. ## Re: following numbers have a mean of 5, find the value of x

No I can't work out what 2x is??

5. ## Re: following numbers have a mean of 5, find the value of x

$\displaystyle \frac{2x+5+2+9+11+1}{7} = 5$

From here, times both sides by 7, then subtract 5+2+9+11+1 from both sides, then divde both sides by 2.

6. ## Re: following numbers have a mean of 5, find the value of x

I'm lost could you show me how that works?

7. ## Re: following numbers have a mean of 5, find the value of x

[How do I solve X?

$5 = \frac{2x}{7}+ \frac{28}{7}$

8. ## Re: following numbers have a mean of 5, find the value of x

Follow these 3 steps.

1. take 28/7 from both sides of the equation
2. Multiply both sides of the equation by 7
3. Divide both sides of the equation by 2