Jill has a circular mirror that measures 18 inches in diameter. what is the area of the mirror in inches?

 
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The area of the circular mirror, in "square inches", is:
  is:  " 254.34  in² " .______________________________________________________
Note:
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diameter, "d" = 18 in. (given) ; 

radius, "r" = "d/ 2 " = "(18 inches) / 2 " =  9 in.  ;
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Area of a circle, "A" :

A =   * r²  ; 

in which:   " A = Area of circle ("plate"); in units of "square inches"; or "in² " ;                    

                  " = 3.14 " {approximation we shall use} ;  

                   "r = radius =  9 in." ; 
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Plug in our known values to solve for the area, "A" :

A = (3.14) * (9 in)² ;

A = (3.14) * (9)² * (in²) ;  A = (3.14) * (9) * (9) * (in²) ;

A = (3.14) * (81) * (in²) ;
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A = 254.34  in²  .
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