Multiple choice

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

  1. 12

  2. 20

  3. 8

  4. 16

Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

For a circle of radius 10 cm (half of diameter 20 cm), the perpendicular distance from center to chord AB is 6 cm. By chord length formula: AB = 2√(r² - d²) = 2√(100 - 36) = 2√64 = 16 cm. Since BC is diameter and AB ∥ CD, chords AB and CD are symmetric about the center. CD is 16 cm - 6 cm = 10 cm from center on the opposite side, giving the same length of 16 cm.