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jmc

prealgebra senior

Problem

Twenty-four 4-inch wide square posts are evenly spaced with 5 feet between adjacent posts to enclose a square field, as shown. What is the outer perimeter, in feet, of the fence? Express your answer as a mixed number.
problem
Solution
There are 20 square posts which are not on a corner, so there are square posts on each side, not including the corner posts. Including the corner posts, there are 7 posts on a side, which means that there are 6 five-foot gaps between posts. Altogether the length of a side is feet. The perimeter of the square is four times the side length, so the perimeter is feet.
Final answer
129\frac{1}{3}