1)What is the area of a regular decagon (12 sides) with side length of 9 cm and apothem of 16.8 cm? Round to the nearest tenth.
2)What is the area of a regular Pentagon with a side of 10 in? Round to the nearest tenth.

Question

1)What is the area of a regular decagon (12 sides) with side length of 9 cm and apothem of 16.8 cm? Round to the nearest tenth.
2)What is the area of a regular Pentagon with a side of 10 in? Round to the nearest tenth.

mehek14 · Answer

Pentagon:
$\dfrac{1}{4}\sqrt{5(5+2√5)}a^2$

mehek14 · Answer

and for #1, decagon is 10 sides
A dodecagon is 12 sides so

$\dfrac{16.8*9}{2}*12$

annalee607 · Answer

What about this one.
Two similar Trapezoids have areas of 432 cm(squared) and 48 cm(squared). What is the ratio of similarity?

mehek14 · Answer

You can do 48:432 and then simplify