# Dice Rolling Covariance

Discrete Mathematics Level pending

A fair, six-sided die is rolled 36 times. What is the covariance between the number of 1s rolled and the number of 2s rolled?

In other words, if $$N_1$$ is the number of 1s and $$N_2$$ is the number of 2s, what is $E(N_1N_2)-E(N_1)E(N_2)?$

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