Math Facts to Memorize for Elementary School

虽然这里要列出的是要熟练记住的, 但是我从来都不鼓励死记硬背。 相反,记忆的过程中我觉得应该鼓励小朋友掌握和理解背后的规律更重要。所以我在列这些常识时,会尽量列出帮助记忆的办法,也就是背后的数学规律。

    • Prime numbers between 1 and 100:

      2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47, 53, 59, 61, 67, 71, 73, 79, 83, 89, 97.

      A prime number is a whole number that only has two factors which are itself and one. A composite number has factors in addition to one and itself.

      The numbers 0 and 1 are neither prime nor composite.

      All even numbers are divisible by two and so all even numbers greater than two are composite numbers.

      All numbers that end in five are divisible by five. Therefore all numbers that end with five and are greater than five are composite numbers.

    • Perfect Squares 1-21:

      number square square root
      1 1 1.000
      2 4 1.414
      3 9 1.732
      4 16 2.000
      5 25 2.236
      6 36 2.449
      7 49 2.646
      8 64 2.828
      9 81 3.000
      10 100 3.162
      11 121 3.317
      12 144 3.464
      13 169 3.606
      14 196 3.742
      15 225 3.873
      16 256 4.000
      17 289 4.123
      18 324 4.243
      19 361 4.359
      20 400 4.472
      21 441 4.583
    • Common Fractions with Decimal and Percent Equivalents

      http://www.factmonster.com/ipka/A0876706.html

      Fraction Decimal Percent
      1/2 0.5 50%
      1/3 0.333… 33.333…%
      2/3 0.666… 66.666…%
      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 0.1666… 16.666…%
      5/6 0.8333… 83.333…%
      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… 11.111…%
      2/9 0.222… 22.222…%
      4/9 0.444… 44.444…%
      5/9 0.555… 55.555…%
      7/9 0.777… 77.777…%
      8/9 0.888… 88.888…%
      1/10 0.1 10%
      1/12 0.08333… 8.333…%
      1/16 0.0625 6.25%
      1/32 0.03125 3.125%