Question

5．直接寫(xiě)出得數(shù)：

5.78+2.16=	18.25-3.3=	3.2-0.02=	25×8=	2÷3=
0.99×9+0.99=	25×0.4=	1×8+1×2=	7÷2.1=	$\frac{2}{5}$×$\frac{2}{5}$÷$\frac{2}{5}$×$\frac{2}{5}$=

Answer 1

分析 計(jì)算小數(shù)的加減法要把小數(shù)點(diǎn)對(duì)齊，按照整數(shù)的加減法的計(jì)算方法計(jì)算，小數(shù)的乘除法按照整數(shù)的乘除法的計(jì)算方法計(jì)算，再看看兩個(gè)因數(shù)一共有幾個(gè)因數(shù)，就從得數(shù)的右邊數(shù)出幾位點(diǎn)上小數(shù)點(diǎn)．

解答 解：5.78+2.16=7.94         18.25-3.3=14.95        3.2-0.02=3.18            25×8=200           2÷3=$\frac{2}{3}$
    0.99×9+0.99=9.9         25×0.4=10          1×8+1×2=10           7÷2.1=$\frac{10}{3}$          $\frac{2}{5}×\frac{2}{5}÷\frac{2}{5}×\frac{2}{5}$=$\frac{4}{25}$

點(diǎn)評(píng) 口算題容易出錯(cuò)，計(jì)算要認(rèn)真，不要抄錯(cuò)數(shù)和運(yùn)算符號(hào)．