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1、1.把下面的小數(shù)化成分?jǐn)?shù),再說一說小數(shù)化分?jǐn)?shù)的方法.0.45 1.2 0.367小數(shù)先化成分母是10,100,1000的分?jǐn)?shù),再約分分?jǐn)?shù)2.先把下面的分?jǐn)?shù)化成小數(shù),再說說分?jǐn)?shù)化小數(shù)的方法.分?jǐn)?shù)小數(shù)用分子除以分母3.把下面各分?jǐn)?shù)改寫成百分?jǐn)?shù).253100212091009100351001121001.81 你能直接判斷 74 ,57.1%,5.7的大小嗎?如果要比較這些數(shù)的大小,需要做些什么?2例1.把0.25,1.4,0.123化成百分?jǐn)?shù).0.2510025=25%1.4104=1014=100140=140%0.1231000123=10012.3=12.3%小數(shù)百分?jǐn)?shù)把小數(shù)點(diǎn)向右移動(dòng)兩位

2、,同時(shí)在后面添上%0.25=25%1.4=140%0.123=12.3%=1=3小數(shù)把小數(shù)點(diǎn)向右移動(dòng)兩位,同時(shí)在后面添上%百分?jǐn)?shù)例2.把27%,124%,0.4%化成小數(shù)。27%=10027=27100=124%=100124=124100=0.4%=1000.4=0.4100=0.00427%=0.27 124%=1.240.4%=0.004把%去掉,同時(shí)把小數(shù)點(diǎn)向左移動(dòng)兩位0.271.2442.把下面各百分?jǐn)?shù)化成小數(shù)。15%80%3.5%1.把下面各小數(shù)化成百分?jǐn)?shù)。0.38 1.05 0.055 3做一做:5例3.把,43,61,153化成百分?jǐn)?shù).43=0.75=75%43=10075=75%610.167=16.7%153=1.6=160%分?jǐn)?shù)百分?jǐn)?shù)通常先化成小數(shù),再化成百分?jǐn)?shù)。6將下列分?jǐn)?shù)化成百分?jǐn)?shù).將下列百分?jǐn)?shù)化成分?jǐn)?shù).518113114%2.5%120%做一做:7例4.你能將17%,40%,12.5%化成分?jǐn)?shù)嗎?17%=1001740%=10040=5212.5%=10012.5=1000125=81百分?jǐn)?shù)分?jǐn)?shù)化成分母是100的分?jǐn)?shù),能約分的要約分8小數(shù)百分?jǐn)?shù)小數(shù)點(diǎn)向右移動(dòng)兩位,添上%去掉%,小數(shù)點(diǎn)向左移動(dòng)兩位.分?jǐn)?shù)通常先化成小數(shù),再化成百分?jǐn)?shù).百分?jǐn)?shù)改寫成分母是100的分?jǐn)?shù),能約分的要約分.9