In the figure above, points A, B, C, and D are collinear and AB, BC, and CD are semicircles with diameters d1cm, d2cm, and d3cm, respectively. What is the sum of the lengths of AB,BC and CD in centimeters?

(1)d1:d2:d3 is 3:2:1

(2)The length of AD is 48 cm.