1. Convert the dimensions of the sheet to inches:
   • 長さ: 4 フィート = 48 インチ
   • 幅: 8 フィート = 96 インチ
2. Convert the thickness to decimal form:
   • 3/16 inch = 0.1875 インチ
3. Calculate the area of the sheet in square inches:
   • Area = Length x Width = 48 inches x 96 inches = 4,608 square inches
4. Calculate the volume of the sheet in cubic inches:
   • Volume = Area x Thickness = 4,608 square inches x 0.1875 inches = 864 立方インチ
5. Convert the volume from cubic inches to cubic feet:
   • Volume (cubic feet) = Volume (立方インチ) / 1728 = 864 立方インチ / 1728 = 0.5 cubic feet
6. Determine the density of aluminum. The density of aluminum is typically around 0.098 ポンド/立方インチ.
7. Multiply the volume in cubic feet by the density to calculate the weight in pounds:
   • Weight (lbs) = Volume (cubic feet) x Density = 0.5 cubic feet x 0.098 lbs/in³ ≈ 0.049 lbs

したがって, a 4×8 3/16 アルミシート would weigh approximately 0.049 ポンド.