let help and step by by explanation

Answer:
225
Step-by-step explanation:
The sides of the small square is 5 m
There are 5 full shaded squares and 8 half squares
Shaded squares = fully shaded small squares + half squares
S = F + H
F = 5x5x5 = 125
H = 8/2 x 5² = 100
S = 100 + 125
S = 225