Asample of copper has a volume of 23.4 cm3 if the density of copper is 8.9 gcm3 what is the coppers mass?

The answer is:  " 208 g " .

Explanation:

The formula/ equation for density is:

D = m / V  ;  That is,  "mass divided by volume" ;
 
Density is expressed as:
   
                   "mass per unit volume";  in which the "mass" is expressed in units of "g" ("grams") ;  and the "unit volume" is expressed in units of:
    "cm³ " or "mL"; 

           {Note the exact equivalent:  1 cm³ = 1 mL }.

         →  The formula is:  " D = m / V "  ; 

   in which:

     "D" refers to the "density" (see above), which is: "8.9 g/cm³ " (given); 

     "m" refers to the "mass" , in units of "g" (grams), which is unknown; and we want to find this value;
                 
     "V" refers to the "volume", in units of "cm³ " ;
               which is:  "23.4 cm³ " (given);

                 We want to find the mass, "m" ; so we take the original equation/formula for the density:
 
              D  =  m / V ; 

             And we rearrange; to isolate "m" (mass) on ONE side of the    equation; and then we plug in our known/given values;
 to solve for "m" (mass);  in units of "g" (grams) ;

    Multiply each side of the equation by "V" ; 

             V * { D  =  m / V } ;  to get:

      V * D = m ;   ↔   m = V * D ;

           Now, we plug in the given values for "V" (volume) and "D" (density) ;     to solve for the mass, "m" ;

           m  =  V * D ;
 
           m  =  (23.4 cm³) * (8.9 g / 1 cm³)  = (23.4 * 8.9) g = 208.26 g ;
  
 →  Round to "208 g" (3 significant figures);  

The answer is:  " 208 g " .

B. a circuit. i think