The radius of the first circle is 4.2 cm, and the diameter of the second is 28 cm. Find the ratio of the areas of these circles.

To find the areas of circles, you need to apply the formula:

S = ПR ^ 2.

The radius of the first circle is 4.2 cm.

Knowing the diameter of the second circle, we find its radius, which is half the value:

28: 2 = 14.

Find the area of the first circle:

S1 = ПR1 ^ 2 = 3.14 * 4.2 ^ 2 = 55.3896.

Find the area of the second circle:

S2 = ПR2 ^ 2 = 3.14 * 14 ^ 2 = 615.44.

Find the area ratio:

S1 / S2 = 55.3896 / 615.44 = 0.09.

Answer: the ratio of the areas of the two circles is 0.09.