1. 直接写出得数。
$2.7×0.2=$
$0.83 + 1.38 =$
$4.8÷0.16 =$
$0.25×3×0.4 =$
$2 - 0.35 =$
$0.25×50 =$
$0.72÷0.8 =$
$2.5 - 0.36 - 0.64 =$
$1.25×4 =$
$14.7 + 3.3 =$
$0.72÷12 =$
$17.64 - 3.5 + 0.36 =$
$30÷50 =$
$0.8×15 =$
$18×0.3 =$
$6.4÷0.8÷2 =$
$3.4 + 5.6 =$
$12×0.2 =$
$1.5×60 =$
$78.5÷0.5×0.01 =$
$1.8×30 =$
$1.22 + 1.4 =$
$10.5 - 5.6 =$
$9×(3.5 + 7.5) =$
$3.2×0.4 =$
$9.6÷8 =$
$10.8 + 2.9 =$
$0.4×0.2 + 1.2 =$
$4.6 - 1.52 =$
$2.9×0.3 =$
$13.6÷0.04 =$
$16.8÷(0.4÷0.5) =$

1. 0.54 2.21 30 0.3
1.65 12.5 0.9 1.5
5 18 0.06 14.5
0.6 12 5.4 4
9 2.4 90 1.57
54 2.62 4.9 99
1.28 1.2 13.7 1.28
3.08 0.87 340 21

2. 解方程。
$32x÷11 = 16$
$5x - 0.5x = 90$
$4x + 3.6÷1.2 = 33$
$44 - x = 28.4$
$4.9 + 5.6x = 32.9$
$1.7×8 - 2x = 6.7$

2. $ x = 5.5 $ $ x = 20 $ $ x = 7.5 $
$ x = 15.6 $ $ x = 5 $ $ x = 3.45 $

已知$x$和$y$是非$0$自然数，且$x + y = 300$，$x$和$y$的最大公因数是$25$，则有几组这样的$x$和$y$？分别是多少？

思维提升
有4组这样的x和y，分别是25和275，125和175，175和125，275和25。