The charge of a drop is the product of number of particles with charge on electron as follows:
[tex]Q = n e[/tex]
Where n is number of electron
e is charge on electron [tex]= 1.6 * 10^-^1^9 C[/tex]
[tex]Q is charge = 4.8 * 10^-^1^9 C[/tex]
[tex]4.8 * 10^-^1^9 = n (1.6 * 10^-^1^9)[/tex]
n = 3
Thus, 3 electrons are present .