What is Unknown (mathematics)?
In [[mathematics]], an '''unknown''' is a number that is not known. Unknown numbers are commonly used in [[algebra]], where they are also known as [[Variable|variables]] . They are represented by symbols such as <math>x</math>, <math>y</math> and <math>z</math>.<ref>{{Cite web|date=2020-03-01|title=Compendium of Mathematical Symbols|url=https://mathvault.ca/hub/higher-math/math-symbols/|access-date=2020-08-16|website=Math Vault|language=en-US}}</ref><ref>{{Cite web|title=Definition of Algebra|url=https://www.mathsisfun.com/definitions/algebra.html|access-date=2020-08-16|website=www.mathsisfun.com}}</ref> In [[science]], an unknown value is represented by a [[letter]] in the [[Roman alphabet|Roman]] or [[Greek alphabet]]. They are used most often in [[physics]], where [[equation]]s are used to describe the relationship between [[physical property|physical properties]]. For example, in the equation <math>E=mc^2</math>, the letter ''<math>m</math>'' represents an unknown (in this case, [[mass]]), and the letter ''<math>E</math>'' also represents an unknown (in this case the amount of [[energy]]). If we know the value of all but one of the unknowns, then we would be able to easily find out the value of the last unknown—by ''solving'' the equation in terms of that last unknown. When letters in science are used this way, not all of them represent unknowns. Some of them might be [[physical constant]]s, which are values that are known to be the same and do not change. In the example above, ''<math>c</math>'' represents a known quantity, the [[speed of light]], which is about 186 thousand [[mile]]s per [[second]].<ref>{{Cite web|last=Redd|first=Nola|date=March 7, 2018|title=How Fast Does Light Travel? {{!}} The Speed of Light|url=https://www.space.com/15830-light-speed.html|archive-url=|archive-date=|access-date=2020-08-16|website=Space.com|language=en}}</ref> And because ''<math>c</math>'' is so large, the formula <math>E=mc^2</math> tells a person who understands algebra that in an atomic reaction, a small amount of m