Let the shorter side of the rectangle be \( x \) and the longer side be \( y \). The diagonal forms a right triangle, and by the Pythagorean theorem:
\[
\text{Diagonal} = \sqrt{x^2 + y^2}
\]
According to the problem, the boy saved half of the longer side, so:
\[
y - \sqrt{x^2 + y^2} = \frac{y}{2}
\]
Solving this equation will give the ratio of \( x \) to \( y \). The correct ratio is \( \frac{2}{3} \).