The ratio between burned-to-unburned is: 1/3.
William made 45 unburned cookies.
Percentage of cookies burned:
[tex]TotalCookies*\frac{1}{3}=CookiesBurned[/tex]And the total cookies is given by:
[tex]TotalCookies=CookiesBurned+CookiesUnburned[/tex]Substituing:
[tex](CookiesBurned+CookiesUnburned)*\frac{1}{3}=CookiesBurned[/tex]Replacing:
[tex](CookiesBurned+45)*\frac{1}{3}=CookiesBurned[/tex]Solving for cookies Burned:
[tex]\begin{gathered} \frac{CookiesBurned}{3}+\frac{45}{3}=CookiesBurned \\ 15=CookiesBurned-\frac{1}{3}CookiesBurned \\ 15=\frac{2}{3}CookiesBurned \\ CookiesBurned=15*\frac{3}{2}=\frac{45}{2} \end{gathered}[/tex]Finally the percentage is given by:
[tex]\frac{CookiesBurned}{TotalCookies}*100[/tex]Replacing:
[tex]\frac{\frac{45}{2}}{(\frac{45}{2}+45)}*100=\frac{1}{3}*100=33.3[/tex]The percentage of Cookies were burned is 33.3%.