Final answer:
Pluto takes longer to orbit the Sun than Earth does because it is much farther away from the Sun, its orbit is more eccentric, and it has a significantly smaller mass.
Step-by-step explanation:
Pluto takes a longer time to travel around the sun than Earth does because its orbital distance from the Sun is much greater. While Earth orbits around the Sun at a distance of 1 AU (Astronomical Unit, the average distance from the Earth to the Sun), Pluto orbits at a distance of about 39 AU. According to Kepler's third law, the farther away a planet is from the Sun, the longer its orbital period, or the time it takes to complete one orbit around the Sun. Additionally, Pluto has a mass that is far less than that of Earth, and it has a more eccentric orbit, which contributes to the long duration of its year, amounting to about 248 Earth years.