I need help with trigonometry problem

Question

A sling is being rotated at the rate of 121 rpm. Give each answer as an exact fraction. 

a)        What will the length of the sling have to be so that the speed of the object at the end will be 38 meters per second? (in meters) 

b)        If the sling is 4 meter long, how fast will the object at the end be traveling? (in meters per second) 

Thank you in advance !

Answer 1

121Rev/min x 2pi rad/1Rev x1 min/60sec = 10pi rad/sec

38m/sec = rx10pi/3 r = 3x38/10pi = 3.63 meters

b) 4 x 10pi/3 = 41.9 m/sec