On a stopwatch, the tip of the second hand moves 2 cm in 15 seconds. How long is the second hand (to the nearest tenth)?
15 seconds is 90o on the clock face
this is 1/4 of the total circumference
circumference = 2 r pi
2 r pi * 1/4 = 2 cm
r = 2cm / (2 pi) * 4 = 1.3 cm