Final answer:
The number of acres in the described parcel of land is 20 acres, by dividing the section into halves and quarters according to the township grid system.
Step-by-step explanation:
To calculate the number of acres in the described parcel of land, we have to break down the divisions mentioned: the NW 1/4 of the SE 1/4 of the E1/2 of Section 21. Each section in a township grid system is a square mile (or 640 acres), according to the provided information.
First, we take the E1/2 (east half) of the section that equates to 320 acres (640 acres / 2). Next, we look at the SE 1/4 (southeast quarter) of that half. This is a quarter of 320 acres, which results in 80 acres (320 acres / 4). Lastly, we have the NW 1/4 (northwest quarter) of the aforementioned SE 1/4. Taking a quarter of 80 acres gives us 20 acres (80 acres / 4).
The correct answer to how many acres are in the parcel of land is 20 acres.