Ok so we know that the distance around the circle (or circumference) is equal to the diameter times pi.
This means that
[tex]37.7 = \pi \times d[/tex]
d being the diameter,
This means that:
[tex]d = \frac{37.7}{\pi} [/tex]
= 12.00028271
= 12 m
So the diameter of the circle is 12 metres.
Hope this helped