Three concentric circles are designed as part of a target practice board. Their diameters form an arithmetic progression. If the smallest circle has a circumference of cm and the largest circle has a circumference of cm, what is the circumference of the middle circle?
Show answer & explanation
Correct answer: C
Explanation
The correct answer is option 3 i.e. 12π cm.
When a, b, c are in AP, b = (a + b)/2
Circumference of circle = π × d
Circumference of smallest circle = 8π
⇒ diameter = 8
Circumference of largest circle = 16π
⇒ diameter = 16
Now, diameter of middle circle = (8 + 16)/2
⇒ 24/2 = 12 cm
Cicumference of middle circle = π × diameter
⇒ 12π