Pyramid Surface Area Ratio

The area of a regular quadrilateral pyramid's mantle is equal to twice its base's area. Calculate the pyramid's surface if the length of the base edge is 20 dm.

Final Answer:

S =  1200 dm²

Step-by-step explanation:

$$\begin{gathered} a=20\text{dm} \\ {S}_1=a^2=20^2=400{\text{dm}}^2 \\ {S}_2=2\cdot S_1=2\cdot 400=800{\text{dm}}^2 \\ S=S_1+S_2=400+800=1200{\text{dm}}^2 \end{gathered}$$

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