Insert a rational number and an irrational number between the following:
$2.357$ and $3.121$

(N/A) rational number is any number that can be expressed in the form $p/q$ where $p$ and $q$ are integers and $q \neq 0$. Since $2.357 < 3 < 3.121$,the integer $3$ is a rational number between $2.357$ and $3.121$.
An irrational number is a number whose decimal expansion is non-terminating and non-recurring. $A$ number like $3.101101110\dots$ satisfies $2.357 < 3.101101110\dots < 3.121$,therefore,it is an irrational number between the given values.