如图，三角形ABC是直角三角形，AB=20米，阴影a面积比阴影b的面积大23平方米，求BC的长度．
涂一涂，在下面的表中表示出算式的结果． （1）× （2）3÷
直接写出得数×=×= 9×=×= 0×= 18×=×=×=×=÷=
算一算，直接写出得数．×= 15÷=+=﹣=×=÷= 0÷=÷=××=÷×=．
直接写出得数．×=÷=﹣= 3.14×40= 75×10%= 3.14×5=÷3﹣= 7×÷7×= 125×1.6= 12.56÷6.28=
计算下面各题． 20×====÷6=×12=÷8= 2﹣=
×
×
=
×
= 9×
=
×
= 0×
=
=
×
=
×
=
×
=
÷
=
×
= 15÷
=
+
=
﹣
=
×
=
÷
= 0÷
=
÷
=
×
×
=
÷
×
=
÷
=
﹣
=
= 7×
÷7×
=
=
=
=
÷6=
÷8= 2﹣
=
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