I have a question on practice question 7 in “Circles, Radians, and a Little More Trigonometry.”

I solved it a different way, but I’m not sure if I was just lucky to get the correct answer. Basically, I figured that, because one radian is when the arc and radius are the same length, that radians are like proportions. So if arc RQ were equal to 6, it would be 6/6, or one radian. So then I divided π by 6 and concluded that’s how many radians it was.

Does that actually work? Or was I just lucky?