Force f acts between two charges, q1 and q2, separated by a distance d.
if q1 is increased to twice its original value and the distance between the charges is also doubled, what is the new force acting between the charges in terms of f?
1/4 f
1/2 f
f
2f

The electrostatic force is proportional to the product of the charges and inversely proportional to the square of the distance that separates the charges.

This is, F = K *Q1 * Q2 / (d^2)

Now, Q1' = 2 * Q1 and d' = 2d

Then F' = K*Q*Q2 / (2d)^2 = K*2Q1*Q2 / 4 (d^2) = 2F / 4 = F/2 = (1/2)F

Then, the answer is the second option of the list. (1/2)F

Where is the table ? you can take a picture of it