Given:

Radius of one of the circles, C₁ = 19 cm = r₁

Radius of the other circle, C₂ = 9 cm = r₂

Let the other circle be C with radius ‘r’.

Circumference of C = Circumference of C₁ + Circumference of C₂ …………(i)

∵ Circumference of circle = 2πr

∴ Circumference of C₁ = 2πr₁ = 2 × × 19 =

and Circumference of C₂ = 2πr₂ = 2 × × 9 =

Using (i), we have

2πr = + =

2 × × r =

r = × × = 28

r = 28 cm

Hence, the radius of the circle is 28 cm.