To simplify the expression \( \frac{t^{400}}{t^{100}} \) using the quotient rule of integer exponents, we apply the rule which states that \( \frac{a^m}{a^n} = a^{m-n} \).
Here, we have:
\[ \frac{t^{400}}{t^{100}} = t^{400 - 100} = t^{300} \]
So the simplified expression is \( t^{300} \).
Therefore, the answer is \( t^{300} \).