To find the expected number of times an even number is rolled on a six-sided number cube, we first identify the even numbers on the cube. The even numbers on a standard six-sided die are 2, 4, and 6.
There are 3 even numbers out of a total of 6 possible outcomes when the die is rolled. Therefore, the probability of rolling an even number in a single roll is:
\[ P(\text{even number}) = \frac{3}{6} = \frac{1}{2} \]
If the die is rolled 30 times, we can calculate the expected number of times an even number will be rolled by multiplying the probability of rolling an even number by the total number of rolls:
\[ \text{Expected number of even rolls} = P(\text{even number}) \times \text{number of rolls} = \frac{1}{2} \times 30 = 15 \]
Thus, you can expect to roll an even number 15 times when rolling the number cube 30 times.