Unknown (math) Facts for Kids

In mathematics, an unknown is a number we do not know. They are commonly used in algebra, where they are also known as variables and represented by symbols such as $x$ , $y$ and $z$ .

In science, an unknown value is represented by a letter in the Roman or Greek alphabet. They are used most often in physics, where equations are used to describe the relationship between physical properties. For example, in the equation $E=mc^2$ , the letter $m$ represents an unknown (in this case, mass), and the letter $E$ 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. Indeed, some of them might be physical constants, which are values that are known to be the same and do not change. In the example above, $c$ represents a known quantity, the speed of light, which is about 186 thousand miles per second. And because $c$ is so large, the formula $E=mc^2$ tells a person who understands algebra that in an atomic reaction, a small amount of mass can produce a very large amount of energy.

Images for kids

The first use of an equals sign, equivalent to 14x + 15 = 71 in modern notation. From The Whetstone of Witte by Robert Recorde of Wales (1557).
The Nine Chapters on the Mathematical Art is an anonymous Chinese book proposing a method of resolution for linear equations.
A conic section is the intersection of a plane and a cone of revolution.
A strange attractor, which arises when solving a certain differential equation

Unknown (math) facts for kids

Related pages

Images for kids

See also