In the diagram, K, O and M are the centers of the three semi-circles. Also, OC = 32 and OM = 36. What is the length of AC?
CM = OM - OC = 36 - 32 = 4
So MB = 4
So OB = OM + MB = 36 + 4 = 40 = the radius of the largest circle
So AO = 40
And AO + OC = 40 + 32 = 72 = AC
