Answer: He needs 7 telephone poles.
Step-by-step explanation:
Length of train track = [tex]5\dfrac{3}{5}\ feet[/tex]
[tex]=\dfrac{5\times5+3}{5}\ feet\\\\=\dfrac{25+3}{5}\ feet\\\\=\dfrac{28}{5}\ feet[/tex]
Distance between two telephone pole = [tex]\dfrac45\ foot[/tex]
Now, Number of telephone poles = (Length of train track) ÷ (Distance between two telephone pole)
[tex]=\dfrac{28}{5}\div \dfrac45\\\\=\dfrac{28}{5}\times \dfrac54\\\\=\dfrac{28}{4}=7[/tex]
So, he needs 7 telephone poles.