SOLUTION: A brass disc has the following dimensions; Diameter; 6'5" Thickness; 4" 5 4" holes. Brass weighs .3 lbs. / cu. in. Determine weight. Volume of cylinder; pi * r^2

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Question 1088573: A brass disc has the following dimensions;
Diameter; 6'5"
Thickness; 4"
5 4" holes.
Brass weighs .3 lbs. / cu. in.
Determine weight.
Volume of cylinder; pi * r^2 * h.
3.1416 * 38.5 * 38. 5 * 4 = 18626.5464 cu. in. (total vol.)
3.1416 * 2 * 2 * 4 = 50.2656 cu. in. (vol. of 1 hole).
50.2656 * 5 = 251.328 cu. in. (vol. of 5 holes).
18626.5464 - 251.328 = 18375.2184 cu. in. (net vol.)
18375.2184 * .3 = 5512.56522 lbs.
Where am I incorrect? Non-homework.
Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
I'll take a slightly different approach
[ net vol ] = [ net area ] x [ height ]
+r%5B1%5D+=+77%2F2+ in
+r%5B1%5D+=+38.5+ in
+pi%2Ar%5B1%5D%5E2+=+3.1416%2A38.5%5E2+
+A%5B1%5D+=+3.1416%2A1482.25+
+A%5B1%5D+=+4656.637+
------------------------
+A%5B2%5D+=+3.1416%2A4%5E2+=+50.2656+
+5%2A50.2656+=+251.328+
+A%5B1%5D+-+5%2AA%5B2%5D+=+4656.637+-+251.328+
+A%5B1%5D+-+5%2AA%5B2%5D+=+4405.309+
------------------------------
+4405.309%2A4+=+17621.236+ net volume
and
+.3%2A17621.236+=+5286.271+ lbs weight
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check my math & formulas