In a circle of diameter 20cm, chords AB and CD are parallel to each other. BC is diameter. If AB is 6 cm from the centre of the circle, what is the length (in cm) of the chord CD ?

16

We know that,

H² = B² + P²

Diameter of the circle = 20 cm

PO = 6cm

AB = CD

OP ⊥ AB

Radius (OB) = \(\frac{20}{7}\) = 10 cm

So, PB = \(\sqrt {10^2 – 6^2}\) = 8cm

So, AB = (PB + PA) = 8 + 8 = 16 cm

CD = AB = 16 cm