To solve the problem using a unit rate, we first need to determine how many school-supply kits the volunteers can put together in one minute.
Given:
- They put together 40 school-supply kits in 8 minutes.
First, we calculate the unit rate (kits per minute):
\[ \text{Kits per minute} = \frac{40 \text{ kits}}{8 \text{ minutes}} = 5 \text{ kits per minute} \]
Now, we want to find out how many kits they can put together in 30 minutes:
\[ \text{Kits in 30 minutes} = 5 \text{ kits per minute} \times 30 \text{ minutes} = 150 \text{ kits} \]
Therefore, the answer is:
150 school-supply kits.