The standard deviation of a number given a percentage is given as;
[tex]\begin{gathered} S\mathrm{}D=\sqrt[]{npq} \\ \text{Where n= sample size} \\ p=\text{ percentage of the customers that order their food to go } \\ q=\text{ percentage of the customers that do not order their food to go} \\ q=1-p \end{gathered}[/tex][tex]\begin{gathered} SD=\sqrt[]{300(0.51)(0.49)} \\ SD=\sqrt[]{74.97} \\ SD=8.66 \end{gathered}[/tex]The standard deviation of the number that order their food to go is 8.66