Question

An object carries a charge of -6.4 µC, while another carries a charge of -2.0 µC. How many electrons must be transferred from the first to the second object so that both objects have the same charge?

Answer 1

if the total charge is -8.4 µC , then each will have -4.2 µC, so it appears that 2.2 µC has to be transfered
Number electrons=2.2 e-6 C/1.6e-19 C=1.37500e13 electrons
check that.

Answer 2

-6.4 + x = -2.0 - x
2 x = 4.4
x = 2.2
so I must add a charge of +2.2*10^-6
and end up with
-4.2*10^-6 on each
now each electron has charge of - 1.6*10^-19 C
so + 2.2*10^-6 = -n (-1.6*10^-16)
( the -n is because I need to subtract a negative charge to get a +x)
n = (2.2 / 1.6) *10^10

Answer 3

Sorry, used 10^-16 instead of 10^-19
should be
(2.2 / 1.6) 10^13