Filling up the tank of a small car cost, in current values, R$ 29.90 in 1972 and R$ 149.70 in 1992. Which of the values below best approximates the percentage increase in the price of gasoline over this 20-year period?
(a) $20 \%$
(b) $125 \%$
(c) $300 \%$
(d) $400 \%$
(e) $500 \%$
The correct option is (d).

Solution 1: The price increase was 149.70 - 29.90 = 119.80 reais, which corresponds to

$$
\frac{119.80}{29.90} \times 100 \% = 400.66 \%
$$

Solution 2: The price practically went from 30 to 150, that is, it was multiplied by 5, which is equivalent to the price going from 100 to 500, representing an increase of $400 \%$.