In the figure, O is the centre of the circle. Its two chords AB and CD intersect each other at the point P within the circle. If AB= 20 cm, PB= 12 cm and CP = 8 cm, then find the measure of PD .

12 cm

According to the concept,

AP x PB = CP x PD

= (AB - PB) x 12 = 8 x PD

= (20 - 12) x 12 = 8 x PD

= 8 x 12 = 8 x PD

= PD = 12

Therefore, PD is 12 cm.