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The effectiveness of the chosen antibiotic or antiseptic can be measured numerically by using the formula \(\pi r^{2}\).

1. For \(\pi\) use 3.14. This value may vary slightly in a specific question.
2. Measure the diameter of the zone of inhibition and divide it by 2. This gives you the radius, \(r\).
3. Use the equation: \(\pi r^{2}\)

The radius is \(\frac{\text{10}}{\text{2}}\) = 5 mm.