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# The radii of two circles are 19 cm and 9 cm respectively. Find the radius of the circle which has circumference equal to the sum of the circumference of the two circles.

$$\therefore$$ $$2 \pi r \ = \ 2 \pi (19) \ + \ 2 \pi (9)$$
$$\Rightarrow \ r \ = \ 19 \ + \ 9 \ = \ 28$$