Rational numbers are those numbers that can be written as a fraction, such as s 7/5 or 3/2.
The symbol ℚ is used for the set of rational numbers and can be thought of as standing
for ‘quotient’ to aid remembering.
A rational number can be defined as a number in the form of x/y where x and y are both members of ℤ and y is not zero. Since a number such as 9 can be written as the fraction 9/1
ℚ includes all members of ℤ. When any rational number is written as a decimal, it either terminates after a finite number of digits (such as 1/8= 0.125) or or recurs (such as 1/3 = 0.333333.....)