1. **State the problem:** We have two quadrilaterals, Q and R. Quadrilateral R is a scaled copy of quadrilateral Q. We know two corresponding side lengths of Q are 9.6 and 10.8, and the corresponding side lengths of R are 7.2 and 8.1. We need to find the scale factor that takes Q to R. 2. **Formula and concept:** The scale factor $k$ between two similar shapes is the ratio of any pair of corresponding side lengths: $$k = \frac{\text{side length of R}}{\text{side length of Q}}$$ 3. **Calculate scale factor using the first pair of sides:** $$k = \frac{7.2}{9.6}$$ Simplify the fraction: $$k = \frac{\cancel{7.2}}{\cancel{9.6}} = \frac{3}{4} = 0.75$$ 4. **Calculate scale factor using the second pair of sides:** $$k = \frac{8.1}{10.8}$$ Simplify the fraction: $$k = \frac{\cancel{8.1}}{\cancel{10.8}} = \frac{3}{4} = 0.75$$ 5. **Conclusion:** Both pairs give the same scale factor $k = 0.75$. This means quadrilateral R is a scaled copy of quadrilateral Q with scale factor 0.75. **Final answer:** $$\boxed{0.75}$$