Any number that can be expressed as a fraction of two integers is called rational. That is, all rational numbers can be put into the form a/b where a and b are both integers. Examples of rational numbers include whole numbers such as 5, integers such as -4, fractions such as 5/7 and decimals with a finite number of decimal places such as 4.31 (which can be written as 431/100). Also, repeating decimals such as 0.18181818… are rational since they can always be written as a fraction (in this case, 18/99). Examples of numbers that are NOT rational include and π, neither of which can be written as a fraction.

Is 3.2 a rational number?

yes

no

Is 4/3 a rational number?

Yes

No

Is -5.321671 a rational number?

Yes

No

Rational numbers can be positive or negative. When writing a negative fraction, it is common to put the “-“ sign in front of the numerator. Note though, that putting the “-“ sign in front of the denominator would mean the same thing since both are divisions involving a positive and negative number. A fraction with a “-“ sign on both the numerator and denominator would actually be positive and so both “-“ signs can simply be removed.