what is meant by variable and constant
A variable can take different values whereas a constant has a fixed value. For example, the lengths of an equilateral triangle can have any values. Therefore, length of an equilateral triangle is a variable. The number of sides of a hexagon is 6, which is fixed. Therefore, the number of sides of a hexagon is a constant. The letters, l, m, n, p, x, y, z, etc., are used to denote variables.