Final answer:
The full capacity of the gas tank is calculated by dividing 9 gallons by 0.30, since 9 gallons represents 30% of the full tank. Hence, the capacity is 30 gallons, which is option B.
Step-by-step explanation:
To determine the capacity of the car's gas tank, we can set up a proportion based on the information that 30% of the tank is filled with 9 gallons of gas. First, we express 30% as a decimal which is 0.30. Then, we can calculate the full capacity of the tank (100%) using a simple equation:
0.30 (Capacity of tank) = 9 gallons
To find the capacity of the tank, we divide both sides by 0.30:
Capacity of tank = 9 gallons / 0.30
Capacity of tank = 30 gallons
Therefore, the full capacity of the gas tank is 30 gallons, which corresponds to option B. 30 gallons.