Variables And Expressions

Variables are the symbols starting with English alphabets used to represent any value which changes from time to time. When these two or more variables are joined together with the help of the symbols are called expressions. For instance V is a symbol to represent any speed, t is the symbol to represent the time. In order to form the formula for acceleration we write:
A = v / t. Here the value of v is divided by t and a = v / t is an expression.

Any expression formed by joining the variable and the mathematical symbols with another variable or a constant value is called a variable expression. These mathematical operators may be addition, subtraction, multiplication and division. Variables and Expressions are co related terms. Expressions cannot be formed without the variables and the mathematical symbols. Variable and expressions join together to form the equations, which have a major role to play in solving the real life problems related to certain expressions.

Let us take an example: to form the variable expression, we need to first understand which symbols are used to represent which words. We must remember the following tips:
+ Sign is used to replace the words Add, Sum, Plus, In All, Increased By, join.
-  Sign is used to represent the words like difference, less, reduced by, subtracted, and decreased by,
X  Sign is used to replace the words like product, multiply , times and,
/ Sign is used to represent the word divide, quotient
Now let us try to form some expressions:
a)      Add a to 5 to get b
We write the above expression as:
=> a + 5 = b
b)      7 is reduced from m to get n,
We write the above expression as:
=> m – 7 = n
c)        The product of x and y is 35,
We write the above expression as:
 => x * y = 35
d)      If t is divided by 3 we get 8,
      We write the above expression as:
=>  t / 3 = 8,
Thus we observe here that x, y, t, m, n, and b are the variables and x-y, t/3 is the expressions. More over they are equated with the equal to sign, so the equations are formed with the support of variables, constants and the mathematical symbols.
The expressions can be evaluated by putting the values of different variables and the values can be attained.
Let us understand it more clearly with an example: Solve x + 2y, when x = 3 and y = 5.
Here putting the values of x and y in the equation x + 2y, we get:
= 3 + 2 * 5,
= 3 + 10,
= 13.
 Again let us try another expression:
Evaluate x – y/2, if x = 7 and y = 2
Putting the value of x and y in the given expression we get,
=  7 – 2/ 2,
= 7 – 1 (as 2/2 is 1),
= 6.