a quarter mile by half mile
1 quarter of a mile square. Each section is 1 mile square so a quarter section is 1/4 mile square.
Any quarter section is comprised of 160 acres.
64.752 hectares in a quarter
You haven't said a 'quarter' of what. If it's a quarter section, then there are 160 acres in it.
Assuming that there is nothing strange going on (e.g. sloppy surveying) there are 40 acres in the quarter-quarter section.
5 / 1/4 = 20 quarter miles in 5 miles.
A kilometer is approximately 2.5 quarter-miles.
That would be a 1/16th quarter: 40 acres.
There are twenty of them.