No. NO. NOOOOO
Use formula Q=It pls. where Q = charge, I = current, t =
time.
Q = It
10^-9 = I x 10^-3
I = 10^-9 / 10^-3 = (using simple indices) = 10^-6 A
Is this your O level year btw? If so, you are in serious danger
of getting screwed physics. Try memorising forumlae to the best of
the ability. All the best.
EDIT: for the second part, use Q = Ne where Q = charge, N =
number of electrons, e = electron charge.
So N = Q / e
Ok?
Eh no. The second solution is from the textbook. I thought there's
something wrong with the explanation since it used 10^-6 and not
10^-9 (that's the main question i want to ask). The first question
was merely there to guide you. (there's the answer just right
beside the question if you didn't see)
Thanks anyway.