a six-sided number cube is to be rolled 30 times. How many times do you expect to roll on an even number.

Since a six-sided number cube has 3 even numbers (2, 4, 6) out of a total of 6 possible outcomes, the probability of rolling an even number is 3/6 or 1/2.

Therefore, if the number cube is rolled 30 times, the expected number of times you would roll an even number is:
(1/2) * 30 = 15 times

So, you would expect to roll an even number 15 times out of 30 rolls.