Answer:
20 fence posts.
Step-by-step explanation:
Calvin is building a fence. The fence will enclose a 100 square foot area, 10 ft wide by 10 ft long. Calvin can put fence posts 2 feet apart.
Now, if he puts a fence post at each corner of the building, then considering each length of the building there will be posts along each length.
Now, considering each width of the building there will be posts (excluding the corner posts) along each width.
Therefore, in total there will be (6 + 6 + 4 + 4) = 20 fence post in the total fence. (Answer)