A street has parallel curbs $36$ feet apart. A crosswalk bounded by two parallel stripes crosses the street at an angle. The length of the curb between the stripes is $20$ feet and each stripe is $45$ feet long. Find the distance, in feet, between the stripes.

Area of the crosswalk parallelogram (curb-segment as base) $=20\times36=720$.

Using the stripe as base: $720=45d$, so $d=\boxed{16}$.