The fence is a rectangle with length of 12 ft and height of 5 ft. It cross wood that form x is like a diagonal of the rectangle. we find the diagonal by using pythagora's theorem.
[tex]\begin{gathered} x^2=a^2+b^2 \\ x^2=12^2+5^2 \\ x^2=144+25 \\ x^2=169 \\ x=\sqrt{169} \\ x=13ft \end{gathered}[/tex]
Total length required for the cross poles = 13 + 13 = 26 ft
