16. (6 points) A store offers a "second cup at half price" promotion for a certain drink. If you buy two cups of this drink, it is equivalent to a discount of... on the original price.

保留源文本的换行和格式如下：

16. (6 points) A store offers a "second cup at half price" promotion for a certain drink. If you buy two cups of this drink, it is equivalent to a discount of... on the original price.
75
【Solution】Solution: Let the price of each cup of this drink be 10, the price for two cups is 20 yuan,
Actually used: $10+10 \times \frac{1}{2}$,
$$
\begin{array}{l}
=10+5, \\
=15 \text { (yuan), }
\end{array}
$$
$15 \div 20=0.75=75 \%$, so it is a 75% discount;
Therefore, the answer is: 75.