To convert pounds to kilograms using the proportion \(1 \text{ kilogram} = 2.2 \text{ pounds}\), we first need to find the conversion factor from pounds to kilograms.
To do that, we can set up the proportion:
\[ \text{kilograms} = \frac{\text{pounds}}{2.2} \]
Now, to find out how many kilograms are equal to 72 pounds, we can substitute 72 for pounds in the equation:
\[ \text{kilograms} = \frac{72 \text{ pounds}}{2.2} \approx 32.727 \]
Rounding to the nearest tenth, we get:
\[ \text{kilograms} \approx 32.7 \]
So the answer is 32.7 kilograms.