Iris completes \( \frac{2}{3} \) of the floor in \( \frac{1}{3} \) of an hour. To find out how long it will take her to complete the entire floor, we can set up a proportion.
If \( \frac{2}{3} \) of the floor takes \( \frac{1}{3} \) of an hour, then for the whole floor (1 full floor), we can calculate the time it takes as follows:
Let \( x \) be the time to complete the entire floor:
\[ \frac{2}{3} \text{ floor} \quad \text{takes} \quad \frac{1}{3} \text{ hour} \]
So, for 1 floor:
\[ 1 \text{ floor} \quad \text{takes} \quad x \text{ hours} \]
Using proportions, we have:
\[ \frac{2/3}{1} = \frac{1/3}{x} \]
Cross-multiplying leads to:
\[ 2x = 1 \]
Solving for \( x \):
\[ x = \frac{1}{2} \text{ hour} \]
Thus, it will take Iris \( \frac{1}{2} \) hours to complete the entire floor.
So, the answer is:
1/2 hours.