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A necklace contains twenty-four spherical beads of silver, each having a radius of 0.5cm. The beads are to be coated, and the cost of coating is $10 per cm2. What is the approximate total cost, to the nearest cent, for coating the beads?     

 

     A_sphere  =  4 π r²     

 

     A_{one bead}  =  (4)(3.1416)(0.5 cm)²     

                      =  (4)(3.1416)(0.25 sqcm)     

                      =  3.1416 sqcm    

 

     A_{24 beads}  =  (24 sqcm)(3.1416)     

                      =  75.3984 sqcm    

 

     Cost  =  (10 $/sqcm)(75.3984 sqcm)     

               =   753.98 $     

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