To calculate the circumference of a circular play mat, you can use the formula:
\[ C = \pi \times d \]
where \( C \) is the circumference and \( d \) is the diameter.
Given that the diameter \( d \) is 6 feet and using \( \pi \approx 3.14 \):
\[ C = 3.14 \times 6 \]
Calculating this:
\[ C = 18.84 \text{ feet} \]
So, the circumference of the play mat, rounded to the nearest hundredth, is 18.84 feet.