You will roll 600 times, of course!
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The expected number of rolls under 3 is the number of rolls times the probability of rolling less than 3. So: E(rolls less than 3 out of 30) = 30 * 1/3 = 30/3 = 10
The expectation is 50 times.
pr(six) = 1/6 → expected 6s in 90 rolls = 1/6 × 90 = 15
Pr(You roll a four in 60 rolls) = 1 - Prob(No fours in 60 rolls) = 1 - [Prob(Not 4 in a roll)]60 = 1 - (5/6)60 = 0.999982 ie 99.9982 per cent
If a DIE (not dice) is rolled 90 times, the expected value of the sum of the first and second rolls is 7 if you assume that the die is fair. It does not matter how many times you roll the die, as long as it is at least 2.