To convert pounds to kilograms using the proportion \(1 \text{ kilogram} = 2.2 \text{ pounds}\), you first need to find how many kilograms are equal to 72 pounds.
Using the conversion, you can set up the equation:
\[ \text{kilograms} = \frac{\text{pounds}}{2.2} \]
Substituting 72 pounds into the equation gives us:
\[ \text{kilograms} = \frac{72}{2.2} \approx 32.727 \]
Rounding to the nearest tenth, we get:
\[ \text{kilograms} \approx 32.7 \]
Thus, the answer is:
32.7