4: 3.14x2x2+3.14x2x2x8
= 3.14x4x2+3.14x2x2x8
=25.12+100.48
=125.6平方分米
5: 花布
18÷2=9
3.14x9x2
=3.14x81x2
=508.68平方厘米
红布
3.14x18x80=4521.6平方厘米
6: 31.4÷2÷3.14=5
3.14x5x2+31.4x31.4
=3.14x25x2+31.4x31.4
=157+985.96
=1142.96平方厘米
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