To convert pounds to kilograms using the proportion \(1 \text{ kilogram} = 2.2 \text{ pounds}\), we can set up the following equation:
\[ \text{kilograms} = \frac{\text{pounds}}{2.2} \]
Now, substituting \(72\) pounds into the equation:
\[ \text{kilograms} = \frac{72}{2.2} \approx 32.727 \]
Rounding to the nearest tenth of a kilogram, we get:
\[ \text{kilograms} \approx 32.7 \]
So, the answer is 32.7 kilograms.