Current location - Training Enrollment Network - Mathematics courses - The perimeter of the Mathematical Pond is 25 1.2m, surrounded by five wide cement roads and a circle of railings on the outside. What is the area of cement road?
The perimeter of the Mathematical Pond is 25 1.2m, surrounded by five wide cement roads and a circle of railings on the outside. What is the area of cement road?
Circumference C=2πR=25 1.2
So r = 25 1.2/2π = 40m.
The area of the cement road is the area of the ring, that is
S=π(40+5)? -πx40x40
=2025π- 1600π
=425π
= 1334.5㎡
The length of the railing is the perimeter of the periphery: