Code:

import sympy

# Define variables for original dimensions
L, W = sympy.symbols('L W', positive=True)
k = 1.5

# Original perimeter
P_original = 2 * (L + W)

# New dimensions
L_new = k * L
W_new = k * W

# New perimeter
P_new = 2 * (L_new + W_new)

# Ratio of perimeters
ratio = P_new / P_original

print(f"{P_original=}")
print(f"{P_new=}")
print(f"{ratio=}")

Output:

P_original=2*L + 2*W
P_new=3.0*L + 3.0*W
ratio=(3.0*L + 3.0*W)/(2*L + 2*W)