We need to look at the triangle, where ramp is a hypotenuse, and 3ft above the ground is an opposite leg.
[tex]sin( \alpha )= \frac{opposite. leg}{hypotenuse}
\\ \\ hypotenuse= \frac{opposite. leg}{sin( \alpha )}
\\ \\ hypotenuse= \frac{3}{sin(4.5^{o})} =38.2(ft)[/tex]
