Two parallel chords are drawn in a circle of diameter 30 cm.  The length of one chord is 24 cm and the distance between two chords is 21 cm.  The length of the other chord is?

18

Use triplets = 9, 12, 15

In Δ AEO

EO = 9 cm

EF = 21 cm (given)

So, OF = 21 - 9 = 12cm

Therefore, In Δ CFO

CF = 9 cm (again using triplets 9, 12, 15)

CD = 9 × 2 = 18 cm