Physics Hwk Problem: Centripetal Acceleration

[shawonna23]

A ceiling fan has two different angular speed settings: w1 = 485 rev/min and w2 = 120 rev/min. What is the ratio (a1/a2) of the centripetal accelerations of a given point on a fan blade?

How would I go about solving this problem?

[Doc Al]

What's the formula for centripetal acceleration? Hint: Find the formula for centripetal acceleration in terms of angular speed (\omega).

[shawonna23]

I used the equation: w^2=a/r. I found the angular speed, but i don't know what the radius is.

[Tide]

The radius will not change between the two speed settings.