Question 1028389
There are three surfaces to consider.
-- exterior surfaces of the wall
-- interior surfaces of the wall
-- top surfaces of the wall
Let's consider the exterior surfaces first.
There are two surfaces that are 200 * 20 ft = 4000 ft^2 each
for a total of 8000 ft^2 .
There are two surfaces that are 300 * 20 ft = 6000 ft^2 each
for a total of 12000 ft^2 .
For the exterior surfaces we have 8000 + 12000 = 20000 ft^2 .
Now consider the interior surfaces of the wall.
There are two surfaces that are (200-(2*1.5)) * 20 ft = 3940 ft^2 each
for a total of 7880 ft^2 .
There are two surfaces that are (300-(2*1.5)) * 20 ft = 5940 ft^2 each
for a total of 11880 ft^2 .
For the exterior surfaces we have 7880 + 11880 = 19760 ft^2 .
Finally consider the top surface.
We can think of two surfaces that are each 200*1.5 or 2*200*1.5 = 600 ft^2
We also have two surfaces (300 - 2*1.5) *1.5 or 2*(300 - 2*1.5) *1.5 = 891 ft^2
The total top surface is 600 + 891 = 1491 ft^2
All together we have 20000 + 19760 + 1491 = 41251 ft^2
Divide by 9 to find yd^2 , 41251/9 = 4583.5 yd^2 approximately
at $3.50 per yd^2 we have 4583.5*3.50 = $16042.25