Triangles \( \Delta ABC \) and \( \Delta DEF \) are similar, which means that the corresponding sides are proportional.
We can find the scale factor (ratio) between the two triangles by comparing the lengths of their corresponding sides. We will calculate the ratios for a pair of corresponding sides.
From the information provided:
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For side \( AC \) in \( \Delta ABC \) and side \( DF \) in \( \Delta DEF \): \[ \frac{DF}{AC} = \frac{8}{16} = \frac{1}{2} \]
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For side \( AB \) in \( \Delta ABC \) and side \( DE \) in \( \Delta DEF \): \[ \frac{DE}{AB} = \frac{11}{22} = \frac{1}{2} \]
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For side \( BC \) in \( \Delta ABC \) and side \( EF \) in \( \Delta DEF \): \[ \frac{EF}{BC} = \frac{12}{24} = \frac{1}{2} \]
All corresponding sides yield the same ratio of \( \frac{1}{2} \).
Thus, the ratio of \( \Delta DEF \) to \( \Delta ABC \) is: \[ \frac{1}{2} \]
Expressed as a fraction in simplest form, the answer is: \[ \boxed{\frac{1}{2}} \]