Since triangles ΔABC and ΔDEF are similar, their corresponding sides are in proportion.
Given that:
- AB corresponds to DF,
- AC corresponds to DE.
We can set up the proportion based on the lengths of sides AB and DF:
\[ \frac{AB}{DF} = \frac{AC}{DE} \]
Substituting the known values:
\[ \frac{16}{3} = \frac{12}{DE} \]
Next, we can cross-multiply to solve for DE:
\[ 16 \cdot DE = 12 \cdot 3 \]
Calculating the right side:
\[ 16 \cdot DE = 36 \]
Now, we divide both sides by 16 to isolate DE:
\[ DE = \frac{36}{16} = \frac{9}{4} = 2.25 \]
Therefore, the length of DE is 2.25.