To find the unit rate of pounds of apples per person, we need to divide the total weight of apples by the number of people.
First, convert \(3 \frac{1}{2}\) pounds into an improper fraction:
\[ 3 \frac{1}{2} = \frac{7}{2} \text{ pounds} \]
Now, we divide this amount by 20 people:
\[ \frac{7/2}{20} = \frac{7}{2} \times \frac{1}{20} = \frac{7 \times 1}{2 \times 20} = \frac{7}{40} \]
So, the unit rate of pounds of apples per person is:
\[ \frac{7}{40} \text{ pounds per person} \]