length of fence in feet suppose that,we have following problem
A straight fence is to be constructed from posts $6$ inches wide and separated by lengths of chain $5$ feet long. If a certain fence begins and ends with a post, which of the following could be the length of the fence in feet? ($12$ inches = $1$ foot). 
possible answers are :
$A. 17$
$B. 28$
$C. 35$
$D. 39$
$E. 50$
basic problem which i have,is understanding of question:
because $12$ inches =$1$feet,it means that $6$inches=$0.5$foot,now we have length  we have $5$ feet and width  $0.5$ width,what is asking exactly question?perimeter?also what does mean that certain fence starts and with a post,does it create something like circle?please help me
 A: It doesn't need to create a circle (it doesn't need to be closed). They're just asking which of the following lengths can be constructed out of increments of 5 and .5, where there is exactly one more post than fence length.
A: It's not saying that it forms a circle. Because it starts with a post and ends with a post, there is one more post than the number of lengths:
$$l=\frac{1}{2}(n+1)+5n$$
Where $n$ is the number of lengths there are (a positive integer).
A: The question says the fence is a straight line. To work as a fence there must be a post at each end, so the number of posts is one more than the number of chains between them. Let $n$ be the number of chains. There is a post for each chain and one post over.
So you have a formula $5.5n+0.5$. Which answer can be written in that form?
A: Suppose n to be the number of chains used for making the fence.Now the length of chain is 5 feet so the length of chain in the fence will be 5 x n.Also 0.5 feet will be length of posts.And fence starts and ends with a post,so chain has to be in between to posts.Thus there will always be n+1 posts in the fence.So the total length of the fence will be 5n + (((n+1) x 0.5).Which can be simplified to 5.5n + 0.5.By putting values in the last equation you will get all the options correct except option C.
