In order to calculate the probability of spending an even number on both sides of the die, we first need to determine the total number of possible outcomes when rolling a six-sided die twice.
When rolling a six-sided die once, there are 6 possible outcomes (numbers 1 through 6).
When rolling the die a second time, there are also 6 possible outcomes.
Therefore, the total number of possible outcomes for rolling the die twice is 6 * 6 = 36.
Next, we need to determine the number of favorable outcomes. In this case, the favorable outcomes are rolling an even number on both sides of the die.
The even numbers on a six-sided die are 2, 4, and 6. Since we want an even number on both rolls, there are 3 even numbers on the first roll and 3 even numbers on the second roll.
Therefore, the number of favorable outcomes is 3 * 3 = 9.
Finally, we can calculate the probability by dividing the number of favorable outcomes by the total number of possible outcomes:
Probability = Number of favorable outcomes / Total number of possible outcomes
Probability = 9 / 36
Probability = 1 / 4
Therefore, the probability of spending an even number on both sides of the die is 1/4.