two circles are tangent to a third circle internally and are tangent to each other externally. The distance between their center are 10 inches, 7 inches and 5 inches. Find their radii

Solution:

The radius are r1,r2,r3

r2 + r3 = 10

r1 - r2 = 7

r1 - r3 = 5

So

r1 = 11

r2 = 4

r3 = 6

So the radius are 11,4,6 inches