Activity- statistics problems

=Problem 1= If n =10, = 12 and = 1530 find coefficient of variation

Solution
$$\frac{\sum x}{n}=\bar x $$

$$\sum {x} ={\bar x \times {n}} $$

$$\sum {x} ={12 \times {10}} $$

$$\sum {x} =120 $$ σ=$$\sqrt{\frac{\sum {x^2}}{n}}-{\frac{({\sum{x}{n})^{2}}}$$