训练积累|小学数学必备数值,记住这些,计算更快更准确
小学数学很难吗?为什么很多孩子学不好数学? 巧妙地记住一些常用的数值,数学就会变得简单而有趣,做题的时候不用计算就能直接写出答案,能节省不少时间。这些数值背下来,以后到了中学,你会发现用处更大了呢~
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% 1/64 =0.015625=1.5625% 1/7 =0.142857142857…≈0.143 =14.3% 2/7 =0.285714285714…≈0.286=28.6% 3/7 =0.428571428571…≈0.429=42.9% 4/7 =0.57142857142…≈0.571=57.1% 5/7 =0.714285714285…≈0.714=71.4% 6/7 =0.857142857142…≈0.857=85.7% 熟记:142857
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 3.14×11=34.54 3.14×12=37.68 3.14×16=50.24 3.14×18=56.52 3.14×20=62.80 3.14×25=78.50 3.14×32=100.48 3.14×36=113.04 3.14×49=153.86 3.14×64=200.96 3.14×81=254.34 3.14×121=379.94
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