SOLUTION: A concrete pipe has length 10 feet, outer diameter 4 feet and thickness 3 inches. To the nearest 100 pounds, how much does it weigh? (Concrete weighs 150 lb/ft3.)

Question 1060496: A concrete pipe has length 10 feet, outer diameter 4 feet and thickness 3 inches. To the nearest 100 pounds, how much does it weigh? (Concrete weighs 150 lb/ft3.)
Found 2 solutions by Alan3354, addingup:
Answer by Alan3354(69443) (Show Source): You can put this solution on YOUR website!
A concrete pipe has length 10 feet, outer diameter 4 feet and thickness 3 inches. To the nearest 100 pounds, how much does it weigh? (Concrete weighs 150 lb/ft3.)
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For a cylinder:

h = 120 inches
---
find the volume of the outside cylinder: r = 24 inches
Subtract the volume of the inside cylinder: r = 18 inches
--> Vol in cubic inches.
---
Multiply volume by density.
1 cu ft = 12*12*12 = 1728 cu inches
150 pounds/cu ft = 150/1728 pounds/cu inch

Answer by addingup(3677) (Show Source): You can put this solution on YOUR website!
Convert everything to inches (1ft = 12in)
Volume: Pi*r^2*length
Pi*24^2*120 = 217146.90 cubic inches
Next:
48-(3*2)= 42 and 42/2=21 is the radius of the empty space inside the tube
Pi*21^2*120 = 166253.08 is the volume of air inside the tube
Next:
217146.90-166253.08 = 50893.82 is the volume of concrete.
1 cubic foot = 1728 in^3
50893.82/1728 = 29.45 cubic feet
29.45*150 = 4417.5 pounds
:
John

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