Question

What is the approximate distance from earth to pluto?

Answer 1

There are two approximations, One is a = 5906.4 M km = 39.48 AU. The other b = 5123.3 M km = 34.25 AU is better, for Pluto with highly eccentric orbit.

Explanation:

In mathematical exactitude, the average distance is semi-minor axis b. For the Earth, the average is defined as 1 AU = b = 149597870 km. For Pluto with orbital eccentricity as high as 0.4976, b = 5123.3 million km = 34.25 AU. I value b as better. . .
Average of perihelion and aphelion (semi-major axis a) is usually given as approximation to distance of a planet from the Sun. '
Anyway, either approximation is also an approximation to the average distance between any inner planet and Pluto.. I had explained this aspect elsewhere, in my answers to similar questions.