Let's put in terms everyone might use understand better. The OP referring to cutting 6/10 of an acre.
Personally I think doing it in 15 minutes is a little unrealistic if you are going to be doing it safely. First any mower needs time for the blades to cut properly. Duller the blades the long it takes. Plus you need a perfectly level lawn with no objects to mow around. If I try mowing as fast as some my customer mowers can move I be bouncing out of the seat. It also depends how much you are taking off the top on each pass.
To be going this fast also means you probably would tearing up the lawn when making turns too. My neighbor's Hustler Super Z can mow very fast but if you try to turn when that fat it simply slides around ripping up grass, plus I might just slam into a tree or other object.
It is also give any figures how many acres as different grasses grow at different rates at any given time. Some grow like weeds in early Spring, other grow rapidly during the seeding times. They faster during humid weather than dry spells. They also like grow rather fast if large amounts are removed at once vs having an inch removed at each time.