百分数、小数和分数的互化

1、百分数和分数、小数的互化,1、百分数与小数的互化,a.把分数化成小数,分数与小数的互化,b.把小数化成分数,a.把分数化成小数,分数与小数的互化,b.把小数化成分数,例1：先把下面的分数化成小数,再说说分数化小数的方法。,分数,小数,用分子除以分母,25,3,100,21,5,2,= 325,= 21100 = 0.21,1,= 75 = 1.4,= 0.12,做一做,4,3,10,7,8,3,= 0.75,= 0.7,1,= 1.375,1.把下面的分数化成小数。,5,6,= 1.2,25,38,= 1.52,25,2,= 0.05,例2：把下面的小数化成分数,再说一说小数化分数的方法。,0

2、.45 1.2 0.367,小数,先化成分母是10,100,1000的分数,再约分,分数,0.45 =,100,45,=,20,9,1.2 =,10,12,=,5,6,0.367 =,1000,367,2.把下面的小数化成分数。,0.27 = 1.52 = 0.08 =,3.25 = 0.75 = 0.005 =,做一做,100,27,25,38,25,4,4,13,4,3,200,1,a.把小数化成百分数,百分数与小数的互化,b.把百分数化成小数,a.把小数化成百分数,百分数与小数的互化,b.把百分数化成小数,例3：把0.25, 1.4, 0.123化成百分数。,0.25,%,1.4 = 1

3、40（ ）,=（ ）,0.123 =12.3（ ）,12.3%,小数,百分数,把小数点向右移动两位,同时在后面添上%,=25%,%,%,=（ ）,140%,= 25（ ）,做一做,3.把下面各小数化成百分数。,0.38 = 1.05 = 0.055 = 3 = 3.28 = 0.08 =,38%,105%,5.5%,300%,328%,8%,例4：把27% ,124% ,0.4%化成小数。,27%=,124%=,0.4%=,0.004,0.27,1.24,小数,百分数,把%去掉，同时把小数点向左移动两位,做一做,4.把下面各百分数化成小数或整数。,15% = 80% = 3.5% = 100%

4、 = 0.4% = 2000% =,0.15,0.8,0.035,1,0.004,20,2、百分数与分数的互化,a.把百分数化成分数,百分数与分数的互化,b.把分数化成百分数,a.把百分数化成分数,百分数与分数数的互化,b.把分数化成百分数,例5：你能将17% ,40% ,12.5%化成分数吗?,17%=,100,17,40%=,100,40,=,5,2,12.5%=,100,12.5,=,1000,125,=,8,1,百分数,分数,化成分母是100的分数,能约分的要约分,做一做,5.将下列百分数化成分数。,14% = 2.5% = 120% = 75% = 0.8% = 5% =,7,50,

5、6,5,1,40,3,4,1,125,1,20,例6：把 ,4,3, ,6,1, 1,5,3,化成百分数。,4,3,=0.75,=75%,6,1,0.167,=16.7%,1,5,3,=1.6=160%,分数,百分数,通常先化成小数,再化成百分数。,除不尽时，通常保留三位小数。,做一做,6.将下列分数化成百分数。,5,1,8,5,1,3,1,4,3,10,7,50,21,4,=20%,=62.5%,133.3%,=75%,=70%,=442%,小数,百分数,分数,总结,小数点向右移动两位,添上%,去掉%,小数点向左移动两位.,通常先化成小数,再化成百分数.,改写成分母是100的分数,能约分的要约分.,先化成分母是10,100,1000的分数,再约分,用分