做大、小两个长方体纸盒,尺寸如下(单位:cm)
????长????宽????高????小纸盒????a????b????c????大纸盒????1.5a????2b????2c(1)做这两个纸盒共用料多少平方厘米?
(2)做大纸盒比做小纸盒多用料多少平方厘米?
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解:(1)2?(1.5a×2b+2b×2c+1.5a×2c)+2(ab+bc+ac),
=2ab+2bc+2ac+6ab+8bc+6ac????????????????????????
=8ab+10bc+8ac(平方厘米)??????????????????????????????????
答:做这两个纸盒共用料(8ab+10bc+8ac)平方厘米?????????????
(2)2?(1.5a×2b+2b×2c+1.5a×2c)-2(ab+bc+ac)??????
=6ab+8bc+6ac-2ab+2bc+2ac???????????????????????????????????????????????
=4ab+6bc+4ac(平方厘米)?????????????????????????????????
答:做大纸盒比做小纸盒多用料(4ab+6bc+4ac)平方厘米???????
解析分析:(1)先求大纸盒的用料2?(1.5a×2b+2b×2c+1.5a×2c),再求出小纸盒的用料2(ab+bc+ac),再相加即可;
(2)用大纸盒的用料2?(1.5a×2b+2b×2c+1.5a×2c)??减去做小纸盒的用料2(ab+bc+ac)即可.
点评:本题考查了列代数式以及合并同类项,是基础知识比较简单.