A standard six-sided number cube (die) has the numbers 1 through 6 on its faces. The even numbers on a six-sided die are 2, 4, and 6.
There are three even numbers out of six total numbers. Therefore, the probability of rolling an even number on a single roll of the die is:
\[ P(\text{even number}) = \frac{\text{Number of even numbers}}{\text{Total numbers}} = \frac{3}{6} = \frac{1}{2} \]
If the die is rolled 30 times, the expected number of times we roll an even number can be calculated by multiplying the total number of rolls (30) by the probability of rolling an even number:
\[ \text{Expected number of even rolls} = 30 \times P(\text{even number}) = 30 \times \frac{1}{2} = 15 \]
So, you can expect to roll an even number 15 times.