Answer:
15 cm
Explanation:
The radius is the distance from the center to the edge of a circle. Because the centers touch each other externally, the distance between the centers would be the distance between the center to the edge of one circle plus the distance between the edge to the center of the other circle. This means that the distance between the centers of the circles would be the radius of one circle plus the radius of the other. (see the attached image)
The radius of one circle is 6 cm, while the radius of the other is 9 cm. The distance between the centers would be:
6 cm + 9 cm = 15 cm.
The distance between the centers would be 15 cm.