Which of the following is a rational number?
A rational number is a number which can be written in the form of pq where p and q are Integers and q is not equal to zero. A number is also said to be rational if the decimal expansion is either terminating or non-terminating recurring in nature. The value of π is 3.14159265358...., the digits neither terminate nor recur and hence not rational. √3 = 1.73205080756887...., the digits again are non-recurring and non-terminating; so it is not rational. 30 is not defined and for a rational number, the denominator should be non-zero. But 312 satisfies all the properties of a rational number.