Question

F is inversely proportional to d^2.

Answer 1

Answer:

11.6

Step-by-step explanation:

F = k/ d^2

where k = proportionality constant

k = Fd^2

k = 5 * 9^2

k = 5*81 = 405

d = (K/F)^1/2

d = (405/3)^1/2

d = 11.62 =11.6

Answer 2

Answer:

11.62

Step-by-step explanation:

F is inversely proportional to d^2, so

$F=\frac{k}{d^2}$

for some constant k.  To find  k  plug in given values for  F  and  d.

$5=\frac{k}{9^2}\\5=\frac{k}{81}\\k=405$

Now you can find d for F = 3.

$3=\frac{405}{d^2}\\\\3d^2=405\\\\d^2=135\\d=\sqrt{135}\approx 11.62$