help please! physics question pt 2

Question

A physics student on a roller coaster uses an instrument to measure a centripetal acceleration of 2.1 g as she rounds a corner. Recall that 1g = 9.81 m/s2. Another student measures the tangential speed to be 20.3 m/s. What is the radius of the turn? Give your answer ...
in terms of meters. Do not include units in your answer. They will be assumed to be meters.
to a precision of tenths of a meter. Use a format like ##.# in your answer.
to an accuracy of 0.2 m. Answers within 0.2 meters of the correct answer will be tolerated.

Answer 1

What does centripetal acceleration equal? From this you can get r. 

Answer 2

V²/R=a

(20.3)²/R = 2.1g  

=>   412.09/R=2.1 x 9.8 

=>   412.09/R=20.58

 

=> R= 412.09/20.58=20.0