please show work for the correct answer

Question

Two point charges attract each other with an electric force of magnitude F. If the charge on one of the particles is reduced to one-third its original value and thedistance between the particles is doubled, what is the resulting magnitude of the electric force between them?

Correct option is

1/12​F

Answer 1

Forig=kQ1Q2/r² ... Fnew=kQ1Q2/3/(2r)² = kQ1Q2/r²/12 = Forig/12