A liter of alcohol costs $\mathrm{R} \$ 0,75$. Maria's car travels $25 \mathrm{~km}$ with 3 liters of alcohol. How many reais will Maria spend on the alcohol needed to travel $600 \mathrm{~km}$?
(a) 54
(b) 72
(c) 50
(d) 52
(e) 45
The correct option is (a).

Solution 1: If in a journey of $25 \mathrm{~km}$ she spends 3 liters, then to travel 100 km Maria will spend $4 \times 3=12$ liters. Therefore, to travel $600 \mathrm{~km}$, the car will spend $6 \times 12=72$ liters. Since each liter costs 0.75 reais, 72 liters will cost $0.75 \times 72=54$ reais.

Solution 2: We can use the rule of three to calculate how many liters will be spent on $600 \mathrm{~km}$. We have:

| 3 liters |  |
| :--- | :--- |
| $x$ liters | $25 \mathrm{~km}$ |
|  | $600 \mathrm{~km}$. |

Since this rule of three is direct, it results in $25 x=3 \times 600$ and, therefore,

$$
x=3 \times \frac{600}{25}=72 \text { liters. }
$$

Since each liter costs 0.75 reais, 72 liters will cost $0.75 \times 72=54$ reais.