Number of spaces would be number of squares - 1
You would have 12 squares and 11 spaces.
Multiply number of each by their size then add the two together:
12 x 7 1/4 = 87 inches
11 x 3 5/16 = 36 7/16 inches
Total = 87 + 36 7/16 = 123 7/16 inches
Answer: 123 7/16 inches