Answer: 29 feet.
Step-by-step explanation: The formula for the circumference of a circle is C = π d. In order to calculate the diameter of the tree we will use the same formula and solve for d.
91 = 3.14 x d
In order to solve for d you need to divide both sides for 3.14:
D = 28.98, rounded to the nearest foot is 29 feet.