How would you change the distance between two charged particles to increase the electric force between them by a factor of 25?

To increase the electric force between two charged particles by a factor of 25, you would need to reduce the distance between them to 1/5 of the original distance. This is because the electric force between two charged particles is inversely proportional to the square of the distance between them. By decreasing the distance, the force will increase by the square of the decrease in distance.