From Wikipedia, the free encyclopedia
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| Cardinal | eighty |
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| Ordinal | 80th
(eightieth) |
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| Numeral system | octogesimal |
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| Factorization | 24 × 5 |
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| Divisors | 1, 2, 4, 5, 8, 10, 16, 20, 40, 80 (10) |
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| Greek numeral | Π´ |
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| Roman numeral | LXXX, lxxx |
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| Binary | 10100002 |
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| Ternary | 22223 |
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| Senary | 2126 |
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| Octal | 1208 |
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| Duodecimal | 6812 |
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| Hexadecimal | 5016 |
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| Armenian | Ձ |
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| Hebrew | פ / ף |
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| Babylonian numeral | 𒐕⟪ |
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| Egyptian hieroglyph | 𓎍 |
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80 (eighty) is the natural number following 79 and preceding 81.
80 is:
- 1 + 1 + 2 + 2 + 4 + 2 + 6 + 4 + 6 + 4 + 10 + 4 + 12 + 6 + 8 + 8 = 80.
- A semiperfect number, since adding up some subsets of its divisors (e.g., 1, 4, 5, 10, 20, and 40) gives 80.[1]
- A ménage number.[2]
- Palindromic in bases 3 (22223), 6 (2126), 9 (889), 15 (5515), 19 (4419), and 39 (2239).
- A repdigit in bases 3, 9, 15, 19, and 39.
- The sum of the first four twin prime pairs:
- (3 + 5) + (5 + 7) + (11 + 13) + (17 + 19) = 80.
The Pareto principle (also known as the 80-20 rule) states that, for many events, roughly 80% of the effects come from 20% of the causes.[3][4]
Every solvable configuration of the 15 puzzle can be solved in no more than 80 single-tile moves.[5]
- ^ "Sloane's A005835: Pseudoperfect (or semiperfect) numbers". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation. Retrieved 2016-05-29.
- ^ "Sloane's A000179: Ménage numbers". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation. Retrieved 2016-05-29.
- ^ Bunkley, Nick (March 3, 2008). "Joseph Juran, 103, Pioneer in Quality Control, Dies". The New York Times.
- ^ "What is 80/20 Rule, Pareto's Law, Pareto Principle". Archived from the original on 2013-01-28. Retrieved 2017-05-20.
- ^ A. Brüngger, A. Marzetta, K. Fukuda, and J. Nievergelt, The parallel search bench ZRAM and its applications, Annals of Operations Research 90 (1999), pp. 45–63.