1. 直接写出得数。
0.29×5=
2.6−1.55=
2.8+5.4=
2.8÷(0.14+0.26)=
64÷0.4=
0.06×90=
5.2×0.8=
9.9+0.51+0.1=
0.9+0.13=
2.35+4.75=
3.9×5=
0.07×0.8×100=
9.8÷49=
3.2−1.68=
1.5÷50=
2.02×9+2.02=
0.34÷1.7=
2.5×0.5=
3.6÷0.03=
12−6.2−3.8=
14.6−6=
9.6÷0.12=
25.4−5.42=
3.91÷(5−1.09)=
9×0.6=
1.35×4=
0.92÷0.04=
2.8÷0.7×20=
$\frac{3}{4} - \frac{4}{7} =$
$\frac{3}{4} ÷ \frac{4}{7} =$
$\frac{3}{4} × \frac{4}{7} =$
$2 - \frac{3}{7} - \frac{3}{4} =$

0.29×5=1.45
2.6−1.55=1.05
2.8+5.4=8.2
2.8÷(0.14+0.26)=7
64÷0.4=160
0.06×90=5.4
5.2×0.8=4.16
9.9+0.51+0.1=10.51
0.9+0.13=1.03
2.35+4.75=7.1
3.9×5=19.5
0.07×0.8×100=5.6
9.8÷49=0.2
3.2−1.68=1.52
1.5÷50=0.03
2.02×9+2.02=20.2
0.34÷1.7=0.2
2.5×0.5=1.25
3.6÷0.03=120
12−6.2−3.8=2
14.6−6=8.6
9.6÷0.12=80
25.4−5.42=19.98
3.91÷(5−1.09)=1
9×0.6=5.4
1.35×4=5.4
0.92÷0.04=23
2.8÷0.7×20=80
$\frac{3}{4} - \frac{4}{7} =\frac{5}{28}$
$\frac{3}{4} ÷ \frac{4}{7} =\frac{21}{16}$
$\frac{3}{4} × \frac{4}{7} =\frac{3}{7}$
$2 - \frac{3}{7} - \frac{3}{4} =\frac{23}{28}$

2. 计算下面各题,怎样算简便就怎样算。
$10.5× 10.1 - 0.1× 10.5$
$3.75× 0.99$
$2.54× 0.4× 0.2× 2.5$
$\frac{16}{25} ÷ [ \frac{4}{9} × ( 3 - \frac{7}{5} ) ]$
$1.37÷ 0.25× 2÷ 4$
$\frac{15}{8} ÷ ( \frac{5}{12} ÷ \frac{1}{8} + \frac{3}{8} )$

$10.5× 10.1 - 0.1× 10.5=105$
$3.75× 0.99=3.7125$
$2.54× 0.4× 0.2× 2.5=0.508$
$\frac{16}{25} ÷ [ \frac{4}{9} × ( 3 - \frac{7}{5} ) ]=0.9$
$1.37÷ 0.25× 2÷ 4=2.74$
$\frac{15}{8} ÷ ( \frac{5}{12} ÷ \frac{1}{8} + \frac{3}{8} )=\frac{45}{89}$

亮亮在一张纸上画了一个小圆和一个大圆，已知小圆与大圆的面积之差是28.26平方厘米，小圆的周长是大圆周长的$\frac{4}{5}$，求小圆的面积。

小圆的半径：大圆的半径=小圆的周长：大圆的周长=4:5
小圆的面积：大圆的面积=$4^2:5^2=16:25$
$28.26÷(25−16)×16=50.24$（平方厘米）