Iris completes \( \frac{2}{3} \) of the floor in \( \frac{1}{3} \) of an hour. We can find out how long it takes her to complete the entire floor by setting up the following proportion.
If \( \frac{2}{3} \) of the floor takes \( \frac{1}{3} \) of an hour, then to find the time \( t \) to complete \( 1 \) whole floor, we can set up the equation:
\[ \frac{2/3}{1/3} = \frac{1}{t} \]
Calculating the left side:
\[ \frac{2/3}{1/3} = 2 \]
This means that completing \( 2/3 \) of the floor takes \( \frac{1}{3} \) of an hour, and the time for a whole floor is \( 2 \times \frac{1}{3} \).
Now, calculating that gives:
\[ t = 2 \times \frac{1}{3} = \frac{2}{3} \text{ hours} + \frac{2}{3} \text{ hours} = 1 \text{ hour} \]
Therefore, it will take Iris \( 1 \) hour to complete the entire floor.
So the answer is:
1 hour