# Binomial Distribution

Suppose $0.6$ of students submit assigned homework on time. In a typical class of $40$ students a professor has assigned homework. If a student submits homework on time, he gets $5$ points. Otherwise he gets $0$ points. Find the variance of the total number of points by all students.

So this is a binomial distribution. The variance is $40(0.6)(0.4)$?

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If $X$ is the total number of points by all students, write $X = \sum_{i=1}^{40} X_i$. I think we can use linearity now. –  Naga Nov 19 '10 at 14:12
So $T = 5I$ so that the variance is $5^{2}(0.4)(0.6)$. Hence it would be $(100)(25)(0.4)(0.6)$? –  PEV Nov 19 '10 at 14:07