The range of an automatic rotary sprinkler irrigation device on the park grassland is 10 meters. What is the area it can spray irrigation? The girth of a small trunk is 125.6cm. The cross-sectional area of the trunk is approximately circular. What is its area?
It's actually a circular area,
The center of the circle is where the jet is
Radius R is its range: r = 10m
So the area of sprinkling irrigation is round
S = π R ^ 2 = 3.14 × 10 ^ 2 = 314 square meters
The radius of the trunk of this tree
=125.6÷(2×3.14)
=125.6÷6.28
= 20 (CM)
The cross-sectional area of the trunk of this tree
=3.14×20×20
= 1256 (cm2)