To simplify the expression \( t^{400} t^{100} \) using the Quotient Rule of Integer Exponents, we can use the property of exponents that states:
\[ a^m \cdot a^n = a^{m+n} \]
where \( a \) is a base and \( m \) and \( n \) are the exponents.
In this case, we have:
\[ t^{400} t^{100} = t^{400 + 100} = t^{500} \]
So the simplified expression is:
\[ t^{500} \]