The 2010 Math Trivia Challenge

Three circles with centers at A, B, C and radii 5, 2, 1,
respectively, are tangent to each other as in the
picture.
Determine the area of the triangle ABC obtained
by joining their vertices
A. 20
B. 4√5
C. 12√7
The sides of the triangle have lengths 3, 6, 7; the half
perimeter is s = (3+6+7)/2 = 8; by Heron’s formula the area is
√((8)(8-3)(8-6)(8-7)) = 4√5.
D. 24
E. NA