In this case let the circles intersect at B and F respectively, as shown in figure below:
Attachment:
Inkedintersecting.gif [ 17.93 KiB | Viewed 7106 times ]
Now line
AC is a perpedicular bisector of BF at point D and AB=15 and BC=25. Hence to find the distance we need to calculate AD and DC.
Now triangle ABD is right triangle AD=
√AB2−BD2=√152−102=11.18Now triangle CBD is right triangle CD=
√BC2−BD2=√252−102=22.91.
Hence total distance AC = 11.18+22.91=34.09.
The portion marked in red are properties of a circle.