Question 979184
Let initial no. pf posts planned =x 
So length of frontage = (x-1)*4  (since no. of gaps between posts will be 1 less than no. of posts)
In actual case, length of frontage = ((x-5)-1)*5
=(x-6)*5
So 
(x-6)*5 = (x-1)*4 
=> x= 26