一、常用分数、小数的互化
1/2 =0.5=50%
1/3 ≈0.333 =33.3%
2/3 ≈0.667=66.7%
1/4 =0.25=25%
3/4 =0.75=75%
1/5 =0.2=20%
2/5 =0.4=40%
3/5 =0.6=60%
4/5 =0.8=80%
1/6 ≈0.167=16.7%
5/6 ≈ 0.833=83.3%
1/8 =0.125=12.5%
3/8 =0.375=37.5%
5/8 =0.625=62.5%
7/8 =0.875=87.5%
1/9 ≈ 0.111=11.1%
1/10 =0.1=10%
1/20=0.05=5%
3/20=0.15=15%
7/20=0.35=35%
9/20=0.45=45%
11/20=0.55=55%
13/20=0.65 =65%
17/20=0.85=85%
19/20=0.95=95%
1/16 =0.0625=6.25%
1/32 =0.03125=3.125%
二、常用圆周率的计算
3.14×1=3.14
3.14×2=6.28
3.14×3=9.42
3.14×4=12.56
3.14×5=15.70
3.14×6=18.84
3.14×7=21.98
3.14×8=25.12
3.14×9=28.26
3.14×10=31.40
三、常用的完全平方数
1²=1
2²=4
3²=9
4²=16
5²=25
6²=36
7²=49
8²=64
9²=81
10²=100
11²=121
12²=144
13²=169
14²=196
15²=225
16²=256
17²=289
18²=324
19²=361
20²=400
四、常用的立方数
1³=1
2³=8
3³=27
4³=64
5³=125
6³=216
7³=343
8³=512
9³=729
10³=1000
11³=1331
12³=1728
13³=2197
14³=2744
15³=3375
16³=4096
17³=4913
18³=5832
19³=6859
20³=8000