A solid sphere of radius R has a total charge Q distributed evenly throughout its volume. What fraction of the total charge is located inside a radius R/2?

Explanation:

Volume charge density ρ = charge / volume

= Q / (4/3 πR³)

total charge is located inside a radius R/2

= volume charge density x volume of sphere of radius R/2

= [Q / (4/3 πR³) ] x 4/3 π(R/2)³

= [Q / (4/3 πR³) ] x 4/3 πR³ x 1/8

= Q / 8

required fraction

= 1/8 .

one "light year" is the distance that light travels, through vacuum, in one julian year.   that's 365.25 days, of 24 hours each.

ingenuity says that the answer is 2.7 m.