question on maths

Question

The gravitational force (F) between two masses is inversely proportional to the square of

the distance (d) between them. If F = 4 when d = 5, calculate:

⦁ F when d = 8

⦁ d when F= 25.

Answer 1

4=k/5^2=k/25, k=100

if d=8 F=100/64=25/16

if F=25, d^2=100/25= 4, d=sqr4= 2

k = a constant always = Fd^2