六年级数学上册圆环的面积易错题型讲解

六年级数学上册圆环的面积易错题型讲解


简介:
S环=πR2-πr2 =π102-π52 =100π-25π =314-78.5 =235.5(cm2) S环=π×(R2-r2) =3.14×(122-82) =3.14×(144-64) =3.14×80 =251.2(cm2) r=6÷2=3cm S环=π×(R2-r2) =3.14×(6×6-3×3) =3.14×27 =84.78(cm2)