If the price of a product increased from 5.00 to 5.55 reais, what was the percentage increase?
In reais, the increase was $5.55 - 5 = 0.55$ and, therefore, the percentage increase was

$$
\frac{0.55}{5}=\frac{0.55 \times 20}{5 \times 20}=\frac{11}{100}=11 \%
$$