Question 1208118
A circular disc of cast iron is 7 ft. in diameter and 1 1/3 in. thick. Determine weight.  

A plate 1 ft. square and 1 in. thick weighs 37.5 lbs.

Area of circle:  pi * r^2.
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              <U>Step by step</U>


(1)  Convert 7 ft to inches: 7 ft = 7*12 = 84 inches.



(2)  Find the area of the circular disk in square inches using the formula.
     Remember that the radius is half of the diameter.



(3)  Find the volume of the circular disk in cubic inches by multiplying its area 
     by the thick, which is 4/3 inches.



(4)  Find the density of the iron in  {{{lbs/in^3}}}  by dividing 37.5 lbs by the area 
     of 1 ft by 1 ft plate, which is 12*12 = 144 square inches.



(5)  To find weight, multiply the volume found in (3) by the density found in (4).
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As you complete, celebrate your victory.



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<U>comment from student</U>: Please check my calculations : 
1) 84 in. 2) 3.1416 * 42 * 42 = 5541.78 = 5542 in.^2 3) 5542 * 1.333 = 7380 in.^3 
4) 37.5 / 144 = .2604 lbs. / ft.^3 5) 7389 * .2604 = 1924.09 = 1924 lbs



<U>My response</U> : &nbsp;&nbsp;I checked your calculations. &nbsp;&nbsp;They are correct.


I am very impressed.  &nbsp;&nbsp;My congratulations &nbsp;! &nbsp;&nbsp;You made great job &nbsp;!