Pi ( π ) approximate the number to the hundredth, ten-thousandths, and one-hundredmillionth.

We know that

The regular decagon can be divided into 10 congruent triangles
so
area regular decagon=10*[area of one triangle]

area triangle=b*h/2
where
b=3.25 m
h is the aphotem
h=5 m
area=3.25*5/2> area=8.125 m²

area regular decagon=10*[8.125]> 81.25 m²

Area=81.3 m²

the answer is
81.3 m²