Question 1048234
Find the area of each washer:
{{{Area = pi*r^2}}}
{{{Area = pi*((3/8)^2 - (5/32)^2)}}}
Area =~ 0.365087 sq inches
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Area of 1000 washers = 365 sq inches = 365/144 = 2.535 sq feet
Weight of 1000 washers = area*2 = 5.07 pounds
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Iron description: 
 18 gauge. 
 3' length, 1" width. 
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3' = 36 inches.
36" - 1/8" = 35 7/8" = 287/8 inches = 574/16".
Center to center of washers is 3/4 + 1/16 = 13/16 inches
(574/16)/(13/16) = 44.15 --> 44 washers per sheet.
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If you mean sheets needed for 1000 washers:
1000/44 = 22.73 --> 23 sheets
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PS  Never heard of "sheet iron."
Sheet steel, but not sheet iron.