cn u tell how we do last part in this part

Hey Akansha,

The last part is calculated in the following manner:
$$\begin{gathered} \sigma =\sqrt{\frac{\sum fX}{n}-{\left(\overline{X}\right)}^2} \\ =\sqrt{\frac{17,750}{60}-{\left(15.83\right)}^2} \\ =\sqrt{295.833-250.58} \\ =\sqrt{45.25} \\ =6.72 \end{gathered}$$