I'd be pretty close to stunned if this actually were the case. I can believe the text maybe isn't talking to you very well. No all books speak to everyone. No worries.My textbook isn't very clear on how to calculate expected values and variance - can someone push me in the right direction?
E[X] = n*p
Var(x) = n*p*q
Where q = 1 - p
That's it. Is that in your book? It had better be, otherwise, why is the author published?
n*(3/5) = 5 ==> n = 5 / (3/5) = 25/3
You tell me about the variance. I hardly can wait to see how the book's answer was created. Maybe I'm not understanding the question.