What is the number of acres in a square mile?

A square mile is a measurement of area that refers to a square with each side measuring one mile in length. To understand how many acres are in a square mile, it's important to note that one mile is equivalent to 5,280 feet.

When calculating the area of a square mile, you would multiply the length and width:

1 mile × 1 mile = 5,280 feet × 5,280 feet = 27,878,400 square feet.

Next, to convert square feet to acres, it's useful to know that one acre is defined as 43,560 square feet. Therefore, to find the number of acres in a square mile, you divide the total square feet by the number of square feet in an acre:

27,878,400 square feet ÷ 43,560 square feet/acre = 640 acres.

This calculation leads to the conclusion that there are 640 acres in one square mile, making this the correct answer. The other options represent incorrect interpretations of area measurement in metric conversions or do not align with the known relationships between miles and acres.