To determine the probability that the second cube will land on an even number, given that the first cube also lands on an even number, we need to start by identifying the even numbers on a standard number cube (or die).
The even numbers on a standard six-sided die are 2, 4, and 6. Therefore, there are 3 even outcomes out of the total 6 possible outcomes when rolling a single die.
Now, since the rolls of the dice are independent events, the probability of the second die landing on an even number is not dependent on the outcome of the first die.
So, the probability that the second cube will land on an even number is simply the probability of rolling an even number with one die:
\[ P(\text{even on second cube}) = \frac{\text{Number of even outcomes}}{\text{Total outcomes}} = \frac{3}{6} = \frac{1}{2} = 0.5. \]
Since we are given that the first cube has already landed on an even number, this does not change the probability of the second cube landing on an even number.
Thus, the answer is:
0.5.