Answer:
5 cm
Step-by-step explanation:
Area of 3 cm circle
A = pi r^2 = pi *3^2 = 9pi
Area of 4 cm circle
A = pi r^2 = pi *4^2 = 16pi
The area of the new circle is 16pi+9pi = 25 pi
25 pi = pi r^2
Divide each side by pi
25 = r^2
Take the square root of each side
sqrt(25) = sqrt(r^2)
5 = r
The radius is 5
