The price of a kilogram of chicken was $R \$ 1.00$ in January 2000, when it started to triple every 6 months. How long will it take for the price to reach $\mathrm{R} \$ 81.00$?
(a) 1 year
(b) 2 years
(c) $2 \frac{1}{2}$ years
(d) 13 years
(e) $13 \frac{1}{2}$ years
The correct option is (b).

Since $81=3^{4}$, the value of the chicken has tripled four times. The number of months that have passed is $4 \times 6=24$ months, that is, two years, meaning that in January 2002, the chicken will reach a price of R\$ 81.00.