如图．ABCD是直角梯形，AB=4，AD=5，DE=3．求：（1）三角形OBC的面积；（2）梯形ABCD的面积．
直接写得数．×4= 6﹣=÷=×=×=÷=÷=÷=
= 2.5== 1== 1×= 3÷1%==．
×0=×=÷=÷=
直接写得数×8=﹣=÷3= 21×= 2÷=÷=×=+=
直接写得数．×6= 30×=÷= 20÷=+=××0=×= 1÷×=﹣50%=÷6=
×4= 6﹣
=
÷
=
×
×
=
÷
=
÷
=
÷
=
= 2.5
=
= 1
=
= 1
×
= 3÷1%=
=．
×0=
=
=
=
×8=
﹣
=
÷3= 21×
=
=
÷
=
×
=
+
=
×6= 30×
=
÷
= 20÷
=
+
=
×
×0=
×
= 1÷
=
﹣50%=
÷6=
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