A race car goes around a level ,circular track with a diameter of 1.00 km at a constant speed of 90.0 km/h. What is the car's centripetal acceleration in m/s2?

What is the formula for centripetal acceleration?

You have three different versions of it:

a_c = \frac{v^2}{r} = r\omega^2 = v\omega

You should know each of those symbols. What do you get as centripetal acceleration?