Respuesta :

Area of a circle is πr^2.

The radius of the smaller circle with diameter 10 cm is 5 cm.

The radius of the larger circle with diameter 20 cm.is 10 cm.

Area of larger circle : Area of smaller circle

Area of larger circle = 100π.

Area of smaller circle = 25π.

Ratio = 100π : 25π or 100π/25π.