52. The figure below shows a flower bed consisting of 3 regions each bordered by garden edging. The edging forms 3 concentric circles with the distance between successive borders equal to the radius, r meters, of the smallest circle. The length of edging needed for the border of the smallest region is 10 meters. What is the total length, in meters, of edging needed for the borders of all 3 regions?

Answer and Explanation

Your Answer is

Correct Answer is G

Explanation

The circumference of a circle is proportional to the radius, and the radius of the middle circle is twice that of the innermost circle, so the circumference of the middle circle is 20; similarly, the circumference of the outermost circle is 30; So the sum of the circumferences of the three circles is 10+20+30=60