一、口算。
$1.65\times0.2=$ $0.3\div0.1=$ $0.2\times0.5\div0.01=$
$7.6\div0.19=$ $9.8 - 0.98=$ $(1 - 0.1)\times0.1=$
$2.81 + 1.9=$ $2.97\div100=$ $0.9\times7 + 13.7=$
$1.3\times0.7=$ $1.43 + 2.6=$ $(6.6 - 2.4)\div3=$
$0.42\div0.3=$ $7.01 - 2.2=$ $20 - 3.7 + 7.3=$
$6.8 + 8.6=$ $9.5\times0.4=$ $1.6\div0.8\times0.5=$
$1.2\div0.05=$ $2.19 - 0.9=$ $1.25\times3.3\times8=$
$0.63 + 0.7=$ $1.5\div0.03=$ $5\times0.75\div0.25=$
$0.8\times0.15=$ $8.76 + 3.24=$ $1.1-(0.6 + 0.4)=$
$4.2 - 0.35=$ $10\times0.82=$ $0.5\times(0.8 + 1.4)=$

0.33 3 10
40 8.82 0.09
4.71 0.0297 20
0.91 4.03 1.4
1.4 4.81 23.6
15.4 3.8 1
24 1.29 33
1.33 50 15
0.12 12 0.1
3.85 8.2 1.1

二、解方程。
$1 - 0.8 + 5x = 3.6$ $7x - 5.3x = 6.8$ $1.4\times8 - 2x = 6$

$x = 0.68$ $x = 4$
$x = 2.6$