Answer
Density = 3.755 $\frac{g}{cm^{3}}$
Work Step by Step
Given :
Mass = 33.42 g
Also, when the pellets are added to water, increase in volume = volume of the pellets, when they are completely submerged in water. (Archimedes principle)
Increase in volume = Final volume - Initial volume
Final volume = 21.6 mL
Initial volume = 12.7 mL
Thus volume of pellets = 21.6 - 12.7 = 8.9 mL
Since 1 mL = 1 $cm^{3}$
Thus, 8.9 mL = 8.9 $cm^{3}$
Since Density = $\frac{Mass}{Volume}$
Thus Density = $\frac{33.42}{8.9}$ = 3.755 $\frac{g}{cm^{3}}$
