2.25x1.8+1.25x0.18
=（2.25×2）×0.9＋（1.25×2）×0.09……变一变，就简便。
=4.5×0.9＋0.25×0.9
=0.9×（4.5＋0.25）
=0.9×4.75
=4.275
好烦啊。2.25x1.8+1.25x0.18=2.25x（1+2x0.2x2） +1.25x（0.1+0.08）=2.25+4.5x0.2x2+0.125+0.1= 2.25+0.9x2+0.125+0.1=2.25+0.9+0.9+0.1+0.125=2.25+1+0.9+0.125=3.25+1.025=4.275
8
8
22.5x0.18+1.25x0.18
=(22.5+1.25)x0.18
=23.75x0.18
=23.75x2x0.09
=47.5x0.09
=4.275
(2.25+0.125)乘以1.8 就可以了
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