Geeky Friday: The eighties!

Everything You Always Wanted to Know About 80 * But Were Afraid to Ask

1) The 40th even number = 80
2) 2 x 40 = 80; 4 x 20 = 80; 5 x 16 = 80; 8 x 10 = 80
3) The 17th abundant number = 80
4) The 57th composite number = 80
5) Sum of the 3rd & 12th abundant numbers = 20 + 60 = 80
Sum of the 11th & 42nd composite numbers = = 20 + 60 = 80
6) Sum of the 2nd through 8th odd numbers = 3 + 5 + 7 + 9 + 11 + 13 + 15 = 80.
7) Sum of the 4th & 8th square numbers = 42 + 82 = 16 + 64 = 80
8) Sum of the 4th square & 4th cube number = 42 + 43 = 16 + 64 = 80
9) Sum of the 5th square numbers & 10th triangular numbers = 25 + 55 = 80
10) Sum of the 11th & 12th lucky numbers = 37 + 43 = 80
11) Sum of the 2nd perfect number & 26th even number = 28 + 52 = 80
12) Sum of the 1st, 3rd, & 21st prime numbers = 2 + 5 + 73 = 80
13) Sum of the 2nd, 4th, 8th, and 10th Fibonacci numbers = 1 + 3 + 21 + 55 = 80
(Leonardo Pisano Fibonacci, 1170-1250)
14) Difference between the 15th & 5th pentagonal numbers, [n(3n-1)/2] = 92 - 12 = 80
15) Square root of 80 = 8.94427
16) Cube root of 80 = 4.30887
17) ln 80 = 4.3820 (natural log to the base e)
18) log 80 = 1.90309 (logarithm to the base 10)
19) Sin 80o = 0.984808
Cos 80o = 0.173648
Tan 80o = 5.671282
20) 1/80 expressed as a decimal = 0.0125
21) The 185th & 186th digits of e = 80
The 249th & 250th digits of e = 80
e = 2.7182818284 5904523536 0287471352 6624977572 4709369995
9574966967 6277240766 3035354759 4571382178 5251664274
2746639193 2003059921 8174135966 2904357290 0334295260
5956307381 3232862794 3490763233 8298807531 9525101901
1573834187 9307021540 8914993488 4167509244 7614606680
(Note: The 99th-108th digits of e = 7427466391 is the first 10-digit prime in
consecutive digits of e. This is the answer to the Google Billboard question
that may lead to a job opportunity at Google.com, San Jose Mercury News, 7-10-2004)
22) The 84th & 85th digits of pi, π = 80
The 105th & 106th digits of pi, π = 80
The 450th & 451st digits of pi, π = 80
23) The 3rd & 4th digits of phi, φ = 80
The 46th & 47th digits of phi, φ = 80
Phi or φ = 1.61803... is a transcendental number,
also called the Golden Ratio (or Golden number).
Leonardo da Vinci (1452-1519) first called it the sectio aurea,
(Latin for the golden section) and related it to human anatomy.
Ratios may be found in the Pyramids of Giza & the Greek Parthenon.
24) Binary number for 80 = 01010000
(Decimal & Binary Equivalence; Program for conversion)
25) ASCII value for 080 = P
(Hexadecimal # & ASCII Code Chart)
26) Hexadecimal number for 80 = 50
(Hexadecimal # & ASCII Code Chart)
27) Octal number for 80 = 120
(Octal #, Hexadecimal #, & ASCII Code Chart)
28) Sum of the edges and corners of a 32-faces
small ditrigonal icosidodecahedron = 60 + 20 = 80
Great Ditrigonal Icosidodecahedron: 32 faces, 60 edges, 20 corners)
29) Sum of the edges and corners of a 24-faces
ditrigonal dodecadodecahedron = 60 + 20 = 80
30) The Greek-based numeric prefix octaconta means 80.
31) The Latin-based numeric prefix octoginti- means 80.
32) The Roman numeral for 80 is LXXX.
33) Ba Shí (8, 10) is the Chinese ideograph for 80.
34) (60, 20) is the Babylonian number for 80
Georges Ifrah, From One to Zero: A Universal History of Numbers,
Penguin Books, New York (1987), pp. 326-327
35) In old Greek tradition, the letter Pi, π, had the numerical value of 80.
(Greek & Hebrew numbering system)
36) In Hebrew, the letter Peh, , has the numerical value of 80.
(Hebrew Gematria = 80)
37) 80 in different languages:
Dutch: tachtig, French: quatre-vingt, German: achtzig, Hungarian: nyolcvan,
Italian: ottanta, Spanish: ochenta, Swahili: themanini, Swedish: åttio
38) An octogenerian is a person who is between 80 and 89 years old.
39) In the British system, there are 80 chains per mile.
There are 4 rods per chain. A chain = 66 feet.