(1)d=2r
=2×2
=4(dm);
c=πd
=3.14×4
=12.56(dm);
s=πr 2
=3.14×2×2
=12.56(dm 2);
(2)c=πd
d=c÷π
=6.28÷3.14
=2(dm);
r=d÷2
=2÷2
=1(dm);
s=πr 2
=3.14×1 2
=3.14(dm 2);
(3)r=d÷2
=8÷2
=4(cm);
c=πd
=3.14×8
=25.12(cm);
s=πr 2
=3.14×4×4
=50.24(cm 2);
填表如下:
(1)d=2r
=2×2
=4(dm);
c=πd
=3.14×4
=12.56(dm);
s=πr 2
=3.14×2×2
=12.56(dm 2);
(2)c=πd
d=c÷π
=6.28÷3.14
=2(dm);
r=d÷2
=2÷2
=1(dm);
s=πr 2
=3.14×1 2
=3.14(dm 2);
(3)r=d÷2
=8÷2
=4(cm);
c=πd
=3.14×8
=25.12(cm);
s=πr 2
=3.14×4×4
=50.24(cm 2);
填表如下: