练习二第1题答案
图一
12÷2=6
3.14x62x2+3.14x12x16
= 3.14x36x2+3.14x12x16
=226.08+602.88
=828.96
图二
3.14x22x2+3.14x2x2x20
=3.14x4x2+3.14x2x2x20
=25.12+251.2
=276.32
练习二第2题答案
20cm=0.2m
3.14x0.2x4=2.512
练习二第3题答案
6÷2=3
3.14x32+3.14x6x1.5
=3.14x9+3.14x6x1.5
=28.26+28.26
=56.52
练习二第4题答案
3.14x22x2+3.14x2x2x8
=3.14x4x2+3.14x2x2x8
=25.12+100.48
=125.6
练习二第5题答案
花布
18÷2=9
3.14x92x2
=3.14x81x2
=508.68
红布
3.14x18x80=4521.6
练习二第6题答案
31.4÷2÷3.14=5
3.14x52x2+31.4x31.4
=3.14x25x2+31.4x31.4
=157+985.96
=1142.96