why r rational numbers not closed under division? why divide a rational number only with 0 why not with another rational number? explain.
For any rational number a, a ÷ 0 is not defined. So, rational numbers are not closed under division.
However, if a rational number is divided by a rational number other than zero then its result would be a defined number(i.e., we got some value after division) which is being closed under division.