Refer to the diagram shown below.
w = 6 7/8 in = 6.875 in, the width of each device.
d = 3 1/2 in = 3.50 in, the space between teo devices.
The total space needed is
D = 4(w+d) + w
= 5w + 4d
= 5*6875 + 4*3.5
D = 48.375 in or 48 3/8 in
Answer: 48 3/8 inches or 48.375 inches
