1、百分數(shù)和小數(shù)、百分數(shù)和小數(shù)、 分數(shù)的互化分數(shù)的互化復習復習把下面小數(shù)化成分數(shù)0.2 1.5 0.375 1.25 0.2151.5 1210.375 381.25141復習復習把下面分數(shù)化成小數(shù)2252110078350.8 225211000.21780.875350.6復習復習把下面各數(shù)寫成百分數(shù)1201007110025010012.510071 71100120100120 250100250 12.510012.5 1把把 0.25 、1.4 、0.123 化成百分數(shù)?；砂俜謹?shù)。0.25 =10025= 25 %1.4 =1041= 140 %1014=0.123 =1000123

2、= 12.3 %1003 .12=想一想想一想怎樣能很快地把小數(shù)化成百分數(shù)？小數(shù)百分數(shù)小數(shù)點向右移動兩位，添上百分號做一做做一做把下面各小數(shù)化成百分數(shù)0.3838 0.0555.5 0.38、 1.05、 0.055、 31.05105 3300 2把把 27% 、124% 、0.4% 化成小數(shù)?；尚?shù)。27% =10027= 27100 = 0.27124% =100124= 124100 = 1.240.4% =1000.4= 0.4100 = 0.004想一想想一想怎樣能很快地把百分數(shù)化成小數(shù)？百分數(shù)小數(shù)去掉百分號，小數(shù)點向左移動兩位做一做做一做把下面各百分數(shù)化成小數(shù)150.1515

3、80 3.5800.83.50.035小結(jié)小結(jié) 把小數(shù)化成百分數(shù)，只要把小數(shù)點向右移動兩位，同時在后面添上百分號；把百分數(shù)化成小數(shù)，只要把百分號去掉，同時把小數(shù)點向左移動兩位小數(shù)百分數(shù)小數(shù)點向右移動兩位，添上百分號去掉百分號，小數(shù)點向左移動兩位例例3 3把 、 、 化成百分數(shù)163513443= 0.7561 0.167= 1.6531= 75%= 16.7%= 160 %想一想想一想怎樣能很快地把分數(shù)化成百分數(shù)？分數(shù)百分數(shù)先把分數(shù)化成小數(shù)，再化成做一做做一做把下面各分數(shù)化成百分數(shù)1815131 0.22015 0.12512.5181.333133.31314把把17%、40% 、12.5%

4、化成分數(shù)?；煞謹?shù)。1001717% =1004040% =52=10012.512.5% =81=想一想想一想怎樣能很快地把百分數(shù)化成分數(shù)？百分數(shù)分數(shù)先把百分數(shù)改寫成分數(shù)再約分做一做做一做把下面各百分數(shù)化成分數(shù)14 2.5 1202.52.51001401414100750120120100151小結(jié)小結(jié) 把分數(shù)化成百分數(shù)，通常先把分數(shù)化成小數(shù)（除不盡時，通常保留三位小數(shù)），再把小數(shù)化成百分數(shù)；把百分數(shù)化成分數(shù)，先把百分數(shù)改寫成分數(shù)，能約分的要約成最簡分數(shù)分數(shù)百分數(shù)先化成小數(shù)，再化成先改寫成分數(shù)再約分2.把下面各百分數(shù)化成小數(shù)。15% 80% 3.5%1.把下面各小數(shù)化成百分數(shù)。0.38 1.05 0.055 3做一做:將下列分數(shù)化成百分數(shù).將下列百分數(shù)化成分數(shù).518113114% 2.5% 120%做一做: 小小 數(shù)數(shù): ( )分分 數(shù)數(shù): ( )百分數(shù)百分數(shù): ( ) 小小 數(shù)數(shù): ( )分分 數(shù)數(shù): ( )百分數(shù)百分數(shù): ( )0101010.220%15小數(shù)百