1. 直接写出得数。
$\frac{15}{30}=\frac{3}{(\_\_\_\_\_\_)}=\frac{(\_\_\_\_\_\_)}{10}$
$\frac{30}{36}=\frac{(\_\_\_\_\_\_)}{12}=\frac{15}{(\_\_\_\_\_\_)}$
$\frac{9}{10}+\frac{3}{10}=$
$\frac{45}{60}=\frac{15}{(\_\_\_\_\_\_)}=\frac{(\_\_\_\_\_\_)}{12}$
$\frac{18}{45}=\frac{2}{(\_\_\_\_\_\_)}=\frac{(\_\_\_\_\_\_)}{15}$
$\frac{31}{12}-\frac{5}{12}=$
$\frac{56}{70}=\frac{(\_\_\_\_\_\_)}{35}=\frac{8}{(\_\_\_\_\_\_)}$
$\frac{36}{72}=\frac{(\_\_\_\_\_\_)}{12}=\frac{18}{(\_\_\_\_\_\_)}$
$\frac{31}{36}-\frac{7}{36}=$
$6.8÷17=$
$10 - 4.03=$
$8.1÷0.9=$
$0.5×(17.8 + 2.4)=$
$3.8×3=$
$5.42×5=$
$13.8÷0.6=$
$12÷(0.2×20)=$
$0.81÷0.27=$
$5.6 + 2.45=$
$3 - 1.82=$
$2.5 - 2.5×0.1=$
$3.92 - 1.89=$
$9.8÷1.4=$
$7.05×20=$
$5.4×0.2×25=$

1. 6 5 10 18 $\dfrac{6}{5}$
20 9 5 6 $\dfrac{13}{6}$
28 10 6 36 $\dfrac{2}{3}$
0.4 5.97 9 10.1
11.4 27.1 23 3
3 8.05 1.18 2.25
2.03 7 141 27

2. 计算下面各题，能简算的要简算。
$5.47 + 2.69 + 4.53$
$8.4×9.8$
$18÷(7.28 + 7.72) + 26.8$
$26.8 - 7.51 - 12.49$
$12.5×3.75×0.8$
$46.5 + 30÷2.5×4.8$

2. 12.69 82.32 28
6.8 37.5 104.1

一个分数的分母比分子大 72，约成最简分数是$\frac{5}{29}$。这个分数是多少？

·思维提升
72÷(29−5)=3
$\dfrac{5}{29}=\dfrac{5×3}{29×3}=\dfrac{15}{87}$