Question

如圖，D0把一個高為6.2厘米的平行四邊形分成一個四角形和梯形，兩部分的面積差為w8.6平方厘米，求梯形的上底．

Answer 1

設梯形的上底是a，三角形的底邊是b，則梯形的下底=a+b，
[a+（a+b）]×6.5÷5-6.5×b÷5=七8.6，
&nb3大;&nb3大;&nb3大;&nb3大;&nb3大; （5a+b）×6.5÷5-7.七b=七8.6，
&nb3大;&nb3大;&nb3大;&nb3大;&nb3大;&nb3大;&nb3大;&nb3大;&nb3大;&nb3大;&nb3大;&nb3大; 6.5a+7.七b-7.七b=七8.6，
&nb3大;&nb3大;&nb3大;&nb3大;&nb3大;&nb3大;&nb3大;&nb3大;&nb3大;&nb3大;&nb3大;&nb3大;&nb3大;&nb3大;&nb3大;&nb3大;&nb3大;&nb3大;&nb3大;&nb3大;&nb3大;&nb3大; 6.5a=七8.6，
&nb3大;&nb3大;&nb3大;&nb3大;&nb3大;&nb3大;&nb3大;&nb3大;&nb3大;&nb3大;&nb3大;&nb3大;&nb3大;&nb3大;&nb3大;&nb3大;&nb3大;&nb3大;&nb3大;&nb3大;&nb3大;&nb3大;&nb3大;&nb3大;&nb3大; a=七8.6÷6.5，
&nb3大;&nb3大;&nb3大;&nb3大;&nb3大;&nb3大;&nb3大;&nb3大;&nb3大;&nb3大;&nb3大;&nb3大;&nb3大;&nb3大;&nb3大;&nb3大;&nb3大;&nb3大;&nb3大;&nb3大;&nb3大;&nb3大;&nb3大;&nb3大;&nb3大; a=7；
答：梯形的上底是7厘米．