一个圆柱，高减少2厘米，表面积就减少18.84平方厘米，这个圆柱的底面积是多少？
直接写出得数（最后4题为估算）：×= 1﹣+= 0.6×= 5.2÷（1+0.3）= 87×22≈ 724÷31≈ 816+991≈ 7.18×5.89≈
直接写得数×=×21=×=×= 32×=×=×=×5=
直接写得数．=======（﹣）×30=
直接写出得数． 14×=×5=×= 12×= 3×= 7×= 4.8+0.82= 3﹣2.7=（+2）×9=（﹣）×2=
口算题．×=×=×9=××0=+=×11= 5﹣﹣=×9×7=
×
= 1﹣
+
= 0.6×
= 5.2÷（1+0.3）=
×
=
×21=
×
=
=
=
×
=
×
=
×5=
=
=
=
=
=
=
=（
﹣
）×30=
=
×5=
×
= 12×
= 3×
=
= 4.8+0.82= 3
﹣2.7=（
+2）×9=（
﹣
）×2=
×
=
×
=
×9=
×
×0=
+
=
×11= 5﹣
﹣
=
×9×7=
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