# 80 (number)

 ← 79 80 81 →
Cardinaleighty
Ordinal80th
(eightieth)
Factorization24 × 5
Divisors1, 2, 4, 5, 8, 10, 16, 20, 40, 80
Greek numeralΠ´
Roman numeralLXXX
Binary10100002
Ternary22223
Octal1208
Duodecimal6812

80 (eighty) is the natural number following 79 and preceding 81.

## In mathematics

80 is:

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]

## In science

Element 80: Mercury (Hg)

## In religion

• According to Exodus 7:7, Moses was 80 years old when he initially spoke to Pharaoh on behalf of his people. Today, 80 years of age is the upper age limit for cardinals to vote in papal elections.

Eighty is also:

## References

1. ^ "Sloane's A005835 : Pseudoperfect (or semiperfect) numbers". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation. Retrieved 2016-05-29.
2. ^ "Sloane's A000179 : Ménage numbers". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation. Retrieved 2016-05-29.
3. ^ Bunkley, Nick (March 3, 2008). "Joseph Juran, 103, Pioneer in Quality Control, Dies". The New York Times..
4. ^ "What is 80/20 Rule, Pareto's Law, Pareto Principle". Archived from the original on 2013-01-28. Retrieved 2017-05-20..
5. ^ 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.