The height of a tree is 10 10 meters long and it grows 1 1 cm in a year. Then its height after one year = 10 10 meters 1 1 cm Its height after 3 3 years = 10 10 meters 3 3 cm Its height after 6 6 years = 10 10 meters 6 6 cm Its height after x x years = 10 10 meters x x cm
Where x x represents an unknown number. From the last line, we can find height of the tree after a certain number of years by taking x x equal to that number. For example, we simply let x=15 x = 15 , 25 25 and 55 55 . Thus, the value of x x depends on our choice. We can give x x any value or number we want. In other words, the value of x x is not fixed, it varies from one situation to the other. Therefore, we call x x a variable whereas 10 10 is a fixed number whole value does not change. So 10 10 therefore is called a constant.
