Multiple choice

A chord of length $12$ cm is at a distance of $8$ cm from the center of a circle. Find the length of a chord of the same circle which is at a distance $6$ cm from the center.

  1. $32$ cm
  2. $20$ cm
  3. $16$ cm
  4. $18$ cm
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Radius^2 = (12/2)^2 + 8^2 = 36 + 64 = 100. Radius = 10. For the second chord at distance 6, (chord/2)^2 = 10^2 - 6^2 = 100 - 36 = 64. Chord/2 = 8, so the chord length is 16.

AI explanation

Using the perpendicular bisector property of a chord, the radius squared equals the distance from the center squared plus half the chord length squared. This gives r^2 = 8^2 + (12/2)^2 = 64 + 36 = 100, so the radius is 10. For a distance of 6 cm, half the new chord length squared is 10^2 minus 6^2, giving 100 minus 36, which equals 64. The square root of 64 is 8, and doubling this gives the full chord length of 16 cm.