Question

The numbers 3,5,6 and 4 have frequencies of x x+2, x-8 and x+6 respectively If their mean is 4 then the value of x is

• A. $5$
• B. $6$
• C. $7$
• D. $4$

Answer 1

The correct option is C $7$

x	f	fx
3	x	3x
5	x+2	5x+10
6	x-8	6x-48
4	x+6	4x+24

$\overline{x}=\frac{\sum fx}{n}$

where n=The sum of the frequency

Given $\overline{x}=4$

$\therefore \overline{4}=\frac{18x-14}{4x}$

$\Rightarrow 16x=18x-14$

$\Rightarrow 16x-14x=-14$

$\Rightarrow -2x=-14$

$\Rightarrow x=\frac{-14}{-2}=7$