1. 直接写出得数。
$16.8÷100=$ $3.2+2.68=$ $10×4.3=$
$0.99+2.32=$ $4.5+65=$ $2×0.25=$
$640÷1000=$ $81÷10=$ $4.2-1.5=$
$1.99+0.76=$ $15.7-0.48=$ $32.8-20.9=$
$213÷10000=$ $0.6×300=$ $1.8×5=$
$0.3+0.6=$ $1.7+0.1=$ $0.32×100=$
$0.58+0.21=$ $9.3-4.3=$ $42×0.2=$
$6.93-1.93=$ $2.5×0.4=$ $2.2÷100=$
$0.8×0.5=$ $10×0.69=$ $6.1×8=$

16.8÷100=0.168 3.2+2.68=5.88 10×4.3=43
0.99+2.32=3.31 4.5+65=69.5 2×0.25=0.5
640÷1000=0.64 81÷10=8.1 4.2-1.5=2.7
1.99+0.76=2.75 15.7-0.48=15.22 32.8-20.9=11.9
213÷10000=0.0213 0.6×300=180 1.8×5=9
0.3+0.6=0.9 1.7+0.1=1.8 0.32×100=32
0.58+0.21=0.79 9.3-4.3=5 42×0.2=8.4
6.93-1.93=5 2.5×0.4=1 2.2÷100=0.022
0.8×0.5=0.4 10×0.69=6.9 6.1×8=48.8

2. 列竖式计算。
$4.5×23.4=$ $2.3×3.08=$ $8.7×4.65=$

23.4
× 4.5
-------
1170
936
-------
105.30
$4.5×23.4=105.3$
3.08
× 2.3
-------
924
616
-------
7.084
$2.3×3.08=7.084$
4.65
× 8.7
-------
3255
3720
-------
40.455
$8.7×4.65=40.455$

3. 把下列分数化成小数，小数化成分数。
$\frac{1}{10}=$ $0.3=$ $\frac{11}{100}=$
$\frac{1}{100}=$ $0.5=$ $\frac{169}{1000}=$
$\frac{1}{1000}=$ $0.127=$ $\frac{2}{10}=$

$\frac{1}{10}=0.1$
$0.3=\frac{3}{10}$
$\frac{11}{100}=0.11$
$\frac{1}{100}=0.01$
$0.5=\frac{1}{2}$
$\frac{169}{1000}=0.169$
$\frac{1}{1000}=0.001$
$0.127=\frac{127}{1000}$
$\frac{2}{10}=0.2$