Answer:

20 units

Step-by-step explanation:

let s = length of 1 side

a = area of the square

p = perimeter of the square

a = s^2 (area formula)

p = 4*s (perimeter formula)

if a = 5p;

s^2 = 5 (4*s)

s^2 = 20s

finding s,

s = 20