One-quarter 46001

Express in square centimeters the surface of a sphere whose radius is equal to one-quarter of the radius of the cone. The diameter of the base of the cone is 20 cm.

Correct answer:

S =  78.5398 cm²

Step-by-step explanation:

$$\begin{gathered} D=20\text{cm} \\ {r}_1=D/2=20/2=10\text{cm} \\ {r}_2=\frac{1}{4}\cdot r_1=\frac{1}{4}\cdot 10=\frac{1\cdot 10}{4}=\frac{10}{4}=\frac{5}{2}=2.5\text{cm} \\ S=4\pi \cdot r_2^2=4\cdot 3.1416\cdot 2.5^2=78.5398{\text{cm}}^2 \end{gathered}$$

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