五上數(shù)學(xué)小數(shù)乘除法簡(jiǎn)便運(yùn)算解題技巧一、類型1：一個(gè)數(shù)除以2、4、81、一個(gè)數(shù)÷2，就等于這個(gè)數(shù)×0.52、一個(gè)數(shù)÷4，就等于這個(gè)數(shù)×0.253、一個(gè)數(shù)÷8，就等于這個(gè)數(shù)×0.12512.8×0.25+7.2÷4＝12.8×0.25+7.2×0.25＝（12.8+7.2）×0.25＝20×0.25＝53.3÷2+6.7×0.5＝3.3×0.5+6.7×0.5＝（3.3+6.7）×0.5＝10×0.5＝512.4÷4+87.6×0.25＝12.4×0.25+87.6×0.25＝（12.4+87.6）×0.25＝100×0.25＝253.3÷8+6.7×0.125＝3.3×0.125+6.7×0.125＝（3.3+6.7）×0.125＝10×0.125＝1.25二、類型2：一個(gè)數(shù)除以0.5、0.25、0.1251、一個(gè)數(shù)÷0.5，就等于這個(gè)數(shù)×22、一個(gè)數(shù)÷0.25，就等于這個(gè)數(shù)×43、一個(gè)數(shù)÷0.125，就等于這個(gè)數(shù)×812.8÷0.25+7.2×4＝12.8×4+7.2×4＝（12.8+7.2）×4＝20×4＝8016.4÷0.5+13.6÷0.5＝16.4×2+13.6×2＝（16.4+13.6）×2＝30×2＝6012.1÷0.25－4.1÷0.25＝12.1×4－4.1×4＝（12.1－4.1）×4＝8×4＝323.3÷0.125+4.7×8＝3.3×8+4.7×8＝（3.3+4.7）×8＝8×8＝64三、綜合練習(xí)1.25×0.64×2.5＝(1.25×0.8)×(2.5×0.8)＝1×2＝20.39×19.9＝0.39×20-0.39×0.1＝7.8－0.039＝7.76115.6×2.1－1.56×11＝15.6×2.1－15.6×1.1＝15.6×(2.1－1.1)＝15.6×1＝15.63.2×0.25×12.5=0.8×4×0.25×12.5＝(12.5×0.8)×(0.25×4)＝10×1＝109+0.9+0.99+0.999+0.9999＝9+1×4-0.1-0.01-0.001-0.0001＝13-0.1111＝12.88898.9×1.01＝8.9×1+8.9×0.01＝8.9+0.089＝8.9897.5×0.8+1.2×12.5+2.5×1.6=2.5×3×0.8+2.5×5×1.2+2.5×1.6＝2.5×(2.4+6+1.6)＝2.5×4＝109.7×9.9+0.97＝9.7×9.9+9.7×0.1＝9.7×(9.9+0.1)＝9.7×10＝9799.9×0.36－0.666×49＝0.333×3×36－0.333×2×49＝0.333×108-0.333×98＝0.333×(108-98)＝0.333×10＝3.337.74×(2.8－1.3)+1