DO NOT EVEN BOTHER WITH THIS GUY'S PROBLEM SET
He is basing all of these "conversion" calculations on dodgy conversion factors, rather than unit cancellation. For example, converting square feet to square meters *should be* squaring the conversion factor between feet and meters and multiplying by that, rather than memorizing another different magic number for area. What about volume? Do we have to memorize another magic number for volume, and have it be off by precisely as much as this guy expects it to be off by? Besides, even if the goal of unit conversion in this guy's mind is to memorize a bunch of different multiplication factors, they won't be right because he insists on exact equality rather than within a tolerance.
Instead of this nonsense, go do a problem set written by someone who understands the material and understands how to do unit tests
/rant