Multiple choice

The lengths of two parallel chords of a circle are $6$ cm and $8$ cm. The smaller chord is at a distance of $4$ cm from the centre,t hen the radius of the circle is?

  1. $10$ cm
  2. $5$ cm
  3. $3$ cm
  4. None of these

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

For a chord of length 6 cm, half the chord is 3 cm. The radius forms a right triangle with legs 3 cm and 4 cm, so r^2 = 3^2 + 4^2 = 25 and r = 5 cm.

AI explanation

Draw a perpendicular from the center O to the 8 cm chord, forming a right triangle where the base is 4 cm and the hypotenuse is the radius r. Because a perpendicular from the center bisects a chord, the base is half of 8 cm, which is 4 cm. Applying the Pythagorean theorem to the smaller chord which is at a distance of 4 cm from the center gives r^2 = 4^2 + 3^2. Therefore, r^2 = 25 and r = 5 cm.