Hi there!
Recall Newton's Law of Universal Gravitation:
![\large\boxed{F_g = (Gm_1m_2)/(r^2)}](https://img.qammunity.org/2022/formulas/physics/high-school/siukvtzyva3ajvwcfkzplv0krxe2ybsw93.png)
G = Gravitational Constant
m1, m2 = mass of objects (kg)
r = distance between objects (m)
There is an INVERSE-SQUARE relationship between the gravitational force and the distance between the objects, so:
![F_g = (Gm_1m_2)/(((1)/(4)r)^2) = F_g = (Gm_1m_2)/((1)/(16)r^2)](https://img.qammunity.org/2022/formulas/physics/high-school/vyksce1o3g5m3yw9vst24rp8lkjwdenqjr.png)
![= 16G(m_1m_2)/(r^2) = 16F_g](https://img.qammunity.org/2022/formulas/physics/high-school/a11cbyvzxxmct2ukcfgzaf0xri85n2dwhv.png)
Thus, the gravitational force between the objects would INCREASE by a factor of 16.