Friday, 21 August 2026

Surface Area of a Regular Dodecadhedron


One of the properties of the number associated with my diurnal age today is that it represents the surface area (rounded to the nearest whole number) of a dodecahedron with an edge of 37 units. The formula and result is shown below where \(n\) represents edge length:$$ \begin{align} \text{Surface Area } &= 3 \times n^2 \times \sqrt{{25} + 10 \times \sqrt{5}} \\ &= 3 \times 37^2 \times \sqrt{25 + 10 \times \sqrt{5}} \text{ when }n=37\\ \\&= 28264.0027368755 \dots \\ \\ &\approx 28264 \end{align}$$What's special about the dodecahedron with an edge of 37 units is how close its exact surface area approaches a whole number. The table below shows the results for edges from 1 to 44:

Edge   With Decimal   Rounded

  1      20.645729      21
  2      82.582915      83
  3      185.81156      186
  4      330.33166      330
  5      516.14322      516
  6      743.24624      743
  7      1011.6407      1012
  8      1321.3266      1321
  9      1672.3040      1672
  10     2064.5729      2065
  11     2498.1332      2498
  12     2972.9849      2973
  13     3489.1282      3489
  14     4046.5628      4047
  15     4645.2890      4645
  16     5285.3066      5285
  17     5966.6156      5967
  18     6689.2161      6689
  19     7453.1081      7453
  20     8258.2915      8258
  21     9104.7664      9105
  22     9992.5327      9993
  23     10921.591      10922
  24     11891.940      11892
  25     12903.581      12904
  26     13956.513      13957
  27     15050.736      15051
  28     16186.251      16186
  29     17363.058      17363
  30     18581.156      18581
  31     19840.545      19841
  32     21141.226      21141
  33     22483.199      22483
  34     23866.462      23866
  35     25291.018      25291
  36     26756.865      26757
  37     28264.003      28264
  38     29812.432      29812
  39     31402.154      31402
  40     33033.166      33033
  41     34705.470      34705
  42     36419.066      36419
  43     38173.953      38174
  44     39970.131      39970

Clearly the dodecahedron with edge of 37 units is a clear winner as it has a surface area that differs by only about 0.003 from its surface area when rounded to the nearest whole number.

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