Question

calculate the length of chord which is at a distance 6cm from the center of diameter 20cm

Answer 1

Diameter = 20 cm
Radius = 20/2 = 10 cm
Distance between chord and centre = 6 cm

[See figure...]

By Pythagoras theorem,
10² = 6² + a²
100 = 36 + a²
100 - 36 = a²
a² = 64
a = √64
a = 8 cm

Length of the chord = a + a = 2a = 2(8) = 16 cm

Hope it helps