Question 1182220
<br>
The area of the ring is 1/3 the area of the circle with radius 12cm, so the area of the inner circle is 2/3 the area of the large circle.<br>
Since the ratio of the areas of the two circles is 2:3, the ratio of the radii of the two circles is the square root of that ratio -- sqrt(2):sqrt(3).<br>
ANSWER: The radius of the inner circle is<br>
{{{12*(sqrt(2)/sqrt(3))}}} = 9.7979..., or 9.78 to 2 decimal places.<br>