Since in 2 2/5 sqft are 15 1/2 tiles, then in 1 square foot, there are:
[tex]\frac{15\frac{1}{2}}{2\frac{2}{5}}[/tex]tiles.
To compute the above division we transform the mixed fractions into improper fractions:
[tex]\begin{gathered} 15\text{ }\frac{1}{2}=\frac{31}{2}, \\ 2\frac{2}{5}=\frac{12}{5}. \end{gathered}[/tex]Therefore:
[tex]\frac{15\frac{1}{2}}{2\frac{2}{5}}=\frac{\frac{31}{2}}{\frac{12}{5}}=\frac{31\times5}{12\times2}=\frac{155}{24}\text{.}[/tex]Answer: 6 11/24 tiles.