Question

Three circles touch each other externally. Their centres make a triangle with sides of 11cm, 15cm and 19cm. What are the radii of the three circles?

Answer 1

draw a diagram. The distance between centers is the sum of the radii, so if the circles have radii a,b,c we have

a+b=11
a+c=15
b+c=19

Now it's easy to figure out a,b,c.