Two identical circles intersect each other such that each passes through the centre of the other. Length of common chord is $16\sqrt{3}$ cm. What is the radius of each circle?
Answer & explanation
Correct answer: option 1

Length of common chord BD is 16\(\sqrt {3 }\)
AC = AB = BC = CD = DA = r
So, ABCD is a rhombus
So, \(\Delta \)ABC & \(\Delta \)ACD are equilateral triangle
Then area of equilateral triangle = \(\frac{\sqrt { 3}}{4}\)\( { (side)}^{3 } \)
= \(\frac{\sqrt { 3}}{4}\)\( { r}^{2} \)
So, sum of area of both triangle
ABC & ADC = 2 x \(\frac{\sqrt { 3}}{4}\) x \( { r}^{2} \)
= \(\frac{\sqrt { 3}}{4}\) \( { r}^{2} \) ..(1)
Now area of rhombus
= \(\frac{1}{2}\) x AC x BD
= \(\frac{1}{2}\) x r x 16\(\sqrt {3 }\)
= 8\(\sqrt {3 }\)r ..(2)
Now equate 1st and 2nd equation
= \(\frac{\sqrt { 3}}{4}\) \( { r}^{2} \) = 8\(\sqrt {3 }\)r
= r = 16 cm.
Therefore, radius = 16 cm.