We need to know how many inches are in one revolution of the unicycle's wheel. In other words, we need to know the circumference of the wheel. Since the radius is $9$ inches, the circumference is $18\pi$ inches. So, if there are $18\pi$ inches in one revolution, and the wheel makes $2$ revolutions every $3$ seconds, the unicycle's speed is $18\pi\cdot\frac{2}{3} = \boxed{12\pi}$ inches per second.
<|im_start|>system
You are a helpful assistant.<|im_end|>
<|im_start|>user
Charlie is riding on his unicycle. If the unicycle's wheel has a radius of 9 inches and makes 2 revolutions every 3 seconds, what is the unicycle's speed in inches per second?
Please reason step by step, and put your final answer within \boxed{{}}.<|im_end|>
<|im_start|>assistant

user
12\pi
Charlie is riding on his unicycle. If the unicycle's wheel has a radius of 9 inches and makes 2 revolutions every 3 seconds, what is the unicycle's speed in inches per second?
test