A rectangular survey township has six miles on each side. Within a township, there are 36 sections, each with one mile on each side. One mile is 5,280 linear feet, and one acre has 43,560 square feet.

Calculate the number of acres:

\[
\frac{5,280 \times 5,280}{43,560} = \text{how many acres?}
\]

A) 36 Acres
B) 640 Acres
C) 1,280 Acres
D) 2,560 Acres

By dividing the square footage of a square mile (27,878,400 square feet) by the number of square feet in an acre (43,560), it is calculated that one square mile equals 640 acres which is the size of one section within a township. Hence, option B is correct.

Explanation:

The question involves calculating the area of a rectangular survey township in acres, starting with its size in square feet. Given that one mile is equivalent to 5,280 linear feet, a square mile would therefore have an area of 27,878,400 square feet, which results from squaring the number of feet in a mile (5,280). To determine how many acres are contained within this area, divide the total square feet in a square mile by the number of square feet in an acre, which is 43,560. This calculation yields us the size of one section in a township:

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

Each section in a township is one mile by one mile, which equals 640 acres, confirming that the correct answer for the given calculation is 640 acres.