Alternatively, if we simplify Australia to a circle, then the moon's radius is equal to Australia's radius.
Therefore, since the (surface) area of a circle is πr^2 and the surface area of a sphere is 4πr^2, the moon has roughly four times the surface area of Australia.
OK, it depends on whether you consider 20.66% a decent proportion or not.
Further: surface area of the moon: 37,930,000 sq km, or 25.47% or the land area of Earth.
Total surface area of Earth is ~500,000,000 km^2
Total land area of Earth is ~150,000,000 km^2 (~.29 Earth)
Australia's land area is ~7,500,000 km^2 (~.015 Earth, 5% of land area)
Moon surface area is ~38,000,000 km^2 (~0.074 Earth, 25% of land area)"The best way to get the right answer on the internet is not to ask a question; it's to post the wrong answer."
38 million km2 (Moon area) : 150 million km2 (land area of the Earth) = 25%