Question 1129384
That given {{{3&1/7}}} is an approximation for {{{pi}}}.


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Find weight of a circular disc of cast iron 7 ft. in diameter and 1 1/3 in. thickness. 
A plate of cast iron 1 ft. square and 1 in. thickness weighs 37.5 lbs. 
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{{{pi*cross((7/2)^2)*(1&1/3)}}}, cubic inches, the circular cast iron disc
No..  Not 7 inches diameter; but "7 feet diameter".



All the rest of this was wrong:
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The described PLATE of cast iron, density:
{{{(37.5*pounds)/(12*inches*12*inches*1*inch)}}}


{{{(37.5/144)(pounds/cubicinch)}}}




The weight of the circular cast iron disc:
{{{(pi*(7/2)^2*(1&1/3)(37.5/144)*pounds)}}}


You can compute the expression how you want.