Element    Percent     Percent of 360° = Angle 
O2          45.6%          .456 × 360° = 164.16° 
Silicon     27.3           .273 × 360° =  98.28°
Alum.        8.4           .084 × 360° =  29.88°
Fe           6.2           .062 × 360° =  22.32°
Ca           4.7           .047 × 360° =  16.92°
Other        7.8           .078 × 360° =  28.08°

Draw the pizza, using a compass for the circle and a protractor
to measure the central angles.  You might also put the 
percentages in the pieces of pie even though I didn't here:

             

Edwin