The price of a kilogram of chicken was $R \$ 1.00$ in January 2000 and began to triple every 6 months. When will it reach $R \$ 81.00$?
(a) 1 year
(b) 2 years
(c) $21 / 2$ years
(d) 13 years
(e) $131 / 2$ years
As $81=3^{4}$, then the value of the franc has tripled 4 times, the number of months elapsed is $4 \times 6=24$ months, that is, 2 years, meaning that in January 2002 the chicken will reach the proposed price. The correct option is (b).