Question

根据条件计算下列各圆的面积 1、r=40cm 2、d=52dm 3、c=219.8

Answer 1

1、r=40cm
40*40*3.14=5024
2、d=52dm r=26 26*26*3.14=2122.64
3、c=219.8 r=219.8÷3.14÷2=35 35*35*3.14=3846.5

Answer 2

pi = 3.14
1, s = pi *r *r = 5024 cm^2
2,s = pi*d*d/4 = 2122.64 dm^2 = 221264 cm^2
3,s = c*c/pi/4 = 3846.5