小学奥数中的常用数据及规律
奥数中的常用数据及规律
1、圆周率常取数据
3.14×1=3.14 3.14×2=6.28 3.14×3=9.42
3.14×4=12.56 3.14×5=15.7 3.15×6=18.84
3.14×7=21.98 3.14×8=25.12 3.14×9=28.26
2、常用特殊数的乘积
25×3=75 25×4=100 25×8=200 125×3=375
125×4=500 125×8=1000 625×16=10000 37×3=111
3、常用平方数
11²=121 12²=144 13²=169 14²=196 15²=225
16²=256 17²=289 18²=324 19²=361 10²=100
20²=400 30²=900 40²=1600 50²=2500 60²=3600
70²=4900 80²=6400 15²=225 25²=625 35²=1225
(1×2+25) (2×3+25) (3×4+25)
45²=2025 55²=3025 65²=4225 75²=5625 85²=7225
(4×5+25) (5×6+25) (6×7+25) (7×8+25) (8×9+25)
4、关于常用分数与小数的互化
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% 1/64 =0.015625=1.5625%
1/2=0.5 1/4=0.25 3/4=0.75 1/5=0.2 2/5=0.4 3/5=0.6
4/5=0.8 1/8=0.125 3/8=0.375 5/8=0.625 7/8=0.875
1/20=0.05 3/20=0.15 7/20=0.35 9/20=0.45 11/20=0.55
1/25=0.04 2/25=0.08 3/25=0.12 4/25=0.16 6/25=0.24
5、常用立方数
1³=1 2³=8 3³=27 4³=64 5³=125
6³=216 7³=343 8³=512 9³=729