Question

HHHHHEEEEELLLLLPPPPPP

Answer 1

The length of an arc is given by θ/360×2πr, where θ is angle subtended by the arc to the center and r is the radius of the circle.
 The length is 12 units, and θ/360 is 1/3
Therefore, 12 = 1/3 × 3.142 ×r
                    r = 12× 3/3.142
                    r = 11.457 units
                      ≈ 11 units