A vial contains 10mL of a solution. If the administered amount is 2.5mL, what percentage of the vial has been used?

To determine what percentage of the vial has been used after administering 2.5 mL from a total of 10 mL, you start by calculating the fraction of the solution that has been used. This is done by dividing the amount administered (2.5 mL) by the total volume of the solution in the vial (10 mL).

The calculation is as follows:

[

\text{Fraction used} = \frac{\text{Amount administered}}{\text{Total volume}} = \frac{2.5 , \text{mL}}{10 , \text{mL}} = 0.25

]

To convert this fraction into a percentage, you multiply it by 100:

[

\text{Percentage used} = 0.25 \times 100 = 25%

]

Therefore, since 25% of the vial has been used after administering 2.5 mL, the correct answer is indeed 25%, confirming the answer chosen is accurate. This percentage shows that a quarter of the total solution has been utilized, which aligns with the calculation performed.