Convert 18 Liters to Milliliters: Metric Volume Conversion

To convert 18 liters to milliliters, we will follow these steps:

• Identify the conversion factor from liters to milliliters.
• Multiply the given number of liters by this conversion factor.

Step 1: The conversion factor is $1 \text{ liter} = 1000 \text{ milliliters}$.

Step 2: Multiply 18 liters by 1000 to convert it to milliliters:

$18 \times 1000 = 18000$ milliliters.

Thus, 18 liters is equal to $18,000$ milliliters.

Therefore, the correct answer is $\text{choice 3}: 18,000 \text{ ml}$. The answer, when compared to the choices, confirms that choice 3 is indeed the correct one.