[proofplan]
Fix a [real number](/pages/1303) $t > 0$. The reciprocal $1/t$ is positive, so the [Archimedean Property](/page/Archimedean%20Property) supplies a natural number $n$ larger than $1/t$. Since both $n$ and $t$ are positive, multiplying and dividing by them preserves the inequality direction and gives $1/n < t$.
[/proofplan]
[step:Apply the Archimedean Property to the reciprocal of $t$]
Let $t \in \mathbb{R}$ satisfy $t > 0$. Define the real number $a := 1/t$. Since $t > 0$, we have $a > 0$. The [Archimedean Property](/theorems/737), applied to the positive real number $a$, gives some $n \in \mathbb{N}$ such that
\begin{align*}
n > a = \frac{1}{t}.
\end{align*}
[/step]
[step:Convert the inequality $n > 1/t$ into $1/n < t$]
Because $n \in \mathbb{N}$, we have $n > 0$. Since also $t > 0$, the product $nt$ is positive. Starting from
\begin{align*}
n > \frac{1}{t},
\end{align*}
multiplying both sides by the positive real number $t$ preserves the inequality direction:
\begin{align*}
nt > 1.
\end{align*}
Dividing both sides by the positive real number $n$ again preserves the inequality direction:
\begin{align*}
t > \frac{1}{n}.
\end{align*}
Equivalently,
\begin{align*}
\frac{1}{n} < t.
\end{align*}
Thus there exists $n \in \mathbb{N}$ such that $1/n < t$, as required.
[guided]
We begin with the inequality obtained from the Archimedean Property:
\begin{align*}
n > \frac{1}{t}.
\end{align*}
The goal is to isolate $1/n$ on one side and $t$ on the other. Since $n \in \mathbb{N}$ and natural numbers are positive, $n > 0$. The hypothesis gives $t > 0$. Therefore multiplying or dividing by either $t$ or $n$ preserves the direction of a strict inequality.
Multiplying the inequality by the positive real number $t$ gives
\begin{align*}
nt > 1.
\end{align*}
Now divide by the positive real number $n$:
\begin{align*}
t > \frac{1}{n}.
\end{align*}
Rewriting the same strict inequality with the smaller quantity first yields
\begin{align*}
\frac{1}{n} < t.
\end{align*}
Thus the natural number $n$ found by the Archimedean Property satisfies the required inequality.
[/guided]
[/step]