3. (6 points) To adapt to market competition, a brand of instant noodles has implemented a "more quantity, no price increase" sales strategy. The specific implementation method is: to increase the weight of each bag of instant noodles by $25 \%$, but keep the selling price of each bag of instant noodles unchanged; this is equivalent to a price reduction of $\qquad$ \% per bag of instant noodles.
【Solution】Solve: $1-1 \div(1+25 \%)$
$$
\begin{array}{l}
=1-80 \% \\
=20 \%
\end{array}
$$

Answer: This is equivalent to a price reduction of $20 \%$ per bag of instant noodles. Therefore, the answer is: 20 .