Answer: 14 square inches
Explanation:
There are 4 lateral faces for each of the three blocks. So that is 4*3 = 12 faces so far. Then there is the top and bottom face of the top and bottom block respectively. This brings the total up to 12+2 = 14 external faces.
Alternatively, we can note how 1 cube has 6 faces. So 3 cubes have 3*6 = 18 faces. However, 4 faces are hidden or they are not external faces when we combine the blocks as the diagram shows. So we have 18-4 = 14 external faces.
No matter which method you use, there are 14 external faces. Each face is 1*1 = 1 square inch, so the total surface area is 14*1 = 14 square inches.
