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Constants
(KS3, Year 7)
The Lesson
A constant is a number with a fixed value - its value does not change.Dictionary Definition
The Merriam-Webster dictionary defines a constant as "a number that is assumed not to change value in a given mathematical discussion."Real Examples of Constants
In algebra, some values always stay the same. They are constants. Numbers are examples of constants - a number can only have one value. 2 can only have a value of 2.
Sometimes we use letters to stand in for constants. These letters will still stand in for a number which will always be the same. For example, π (pi) always has a value of 3.14.
In algebra, numbers that are not constants are called variables - they can change in value.
Understanding Constants
It is easier to understand constants with an example. Let's look at an algebraic equation. Consider a linear equation:
The 2 and the 1 are both constants. They both have a fixed value.
The x and the y are variables. We can change their value.
The values of x and y must keep both sides of the equation the same. The left hand side (y) must be the same as the right hand side (2x + 1).
x = 1 ∴ y = 2x + 1 = 2 × 1 + 1 = 3
x = 2 ∴ y = 2x + 1 = 2 × 2 + 1 = 5
x = 3 ∴ y = 2x + 1 = 2 × 3 + 1 = 7
The constants are the same in each case and show which pairs of x and y are allowed by the equation.
Different constants would mean different pairs of x and y would be allowed by the equation.
Coefficients Are a Type of Constant
A constant in front of a variable is called a coefficient. For example, consider the equation shown below:
2 and 1 are both constants in this equation.
The 2 is in front of the x. 2 is the coefficient of x. It means 2 × x.
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See Also
What is algebra? What is a variable? What is a coefficient? What is pi?The Test
Here are 3 randomly selected questions from a larger test that can be printed to create a handout or sent to students electronically.
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