we will consider that the tree trunk is a cylinder with height h = 15 ft and circumference C = 4.5 feet

the circumference C = 2*r*pi, where r is the radius of the base thus we have

2*r*pi = 4.5 divide both sides by 2*pi

r = 4.5/(2*pi)

the volume of the cylinder is V = r^2*pi*h

V = (4.5/(2*pi))^2*pi*h

V = (20.25/(4*pi))*15

V = 75.9375 pi ft^3

pi = 3.14

V = 238.44375 ft^3

the approximate volume of the tree trunk is 238.44375 ft^3.