#### Answer

WIth 1 cup of butter, you can make 24 total (whole) brownies.

#### Work Step by Step

If $\frac{2}{3}$ cup of butter will make 16 brownies, then 1 cup of butter makes 24 brownies. We get 24 by setting up a ratio of 16 brownies to $\frac{2}{3}$ cup of butter.
This ratio is 16 $\div$ $\frac{2}{3}$
In fraction division, we keep the first number (in our case 16), flip the second number (in our case, we flip $\frac{2}{3}$ and get $\frac{3}{2}$) and we change the $\div$ sign to a $\times$ sign. In other words, we multiply by the reciprocal of the second fraction.
Thus, we have:
$\frac{16}{1}$ x $\frac{3}{2}$ = $\frac{48}{2}$ = 24.
24 times the 1 cup of butter given still gives us 24. Therefore, 24 brownies can be made with 1 cup of butter.