By formula,
[tex]\begin{gathered} Z=\frac{X-\mu}{\sigma} \\ \text{Where Z=2.15 , X }=\text{ 479, }\mu=436,\text{ and }\sigma=? \end{gathered}[/tex]Substituting these values into the above formula, we get
[tex]\begin{gathered} 2.15=\frac{479-436}{\sigma} \\ \text{Cross multiplying, we get} \\ 2.15\sigma=43 \\ \text{Dividing both sides by 2.15, we get} \\ \sigma=\frac{43}{2.15}=20\text{ }\approx\text{ 20.0 (to one decimal place)} \end{gathered}[/tex]The correct answer is 20.0 ( to one decimal place)
