How many tons of lignite are contained in a reserve of 1000 acres with beds averaging 20 feet thick, with a specific gravity of 1.28?

To determine the number of tons of lignite in a reserve, the calculation involves several steps related to volume and density. First, calculate the volume of the lignite reserve:

1. Area Conversion: 1 acre equals 43,560 square feet. Thus, 1000 acres equals 1000 x 43,560 = 43,560,000 square feet.

2. Volume Calculation: The thickness of the lignite bed is 20 feet. Therefore, the volume of lignite can be calculated as:

[

\text{Volume} = \text{Area} \times \text{Thickness} = 43,560,000 , \text{ft}^2 \times 20 , \text{ft} = 871,200,000 , \text{ft}^3

]

3. Weight Calculation: To find the weight of the lignite, you need to convert the volume into weight using the specific gravity, which indicates that the material is 1.28 times as heavy as water. Since the density of water is approximately 62.4 lbs/ft³:

[

\text{Density of Lignite