The distance that the train travels is 18.84 feet
Solution:
Given that,
A play train travels around a Christmas tree in a circle
The train track measures 6 feet in diameter
To find: distance that the train travels
The distance the train travels is equal to the circumference of circle
The circumference of circle is given as:

Where, "d" is the diameter of circle
From given,
d = 6 feet

Thus the train travels 18.84 feet