To find out how long it will take him to make 10 waffles, we first determine the time it takes to make 1 waffle.
He takes 9 minutes to make 3 waffles, so the time per waffle is:
\[ \text{Time per waffle} = \frac{9 \text{ minutes}}{3 \text{ waffles}} = 3 \text{ minutes per waffle} \]
Now, to find the time to make 10 waffles, we multiply the time per waffle by the number of waffles:
\[ \text{Time for 10 waffles} = 10 \text{ waffles} \times 3 \text{ minutes per waffle} = 30 \text{ minutes} \]
Thus, it will take him 30 minutes to make 10 waffles.