2πr+2r=41.4
(π+1)r=20.7
r=20.7/(π+1)
圆的周长是:2πr=2π×20.7/(π+1)=41.4π/(π+1)
圆的面积是:πr^2=π×[20.7/(π+1)]^2=428.49π/[(π+1)^2]
如果取π=3.14,代入上式,有:
圆的周长是:41.4π/(π+1)=41.4×3.14/(3.14+1)=31.4
圆的面积是:428.49π/[(π+1)^2]=428.49×3.14/[(3.14+1)^2]=78.5
即:所求周长为31.4、所求面积为78.5.