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 first need to understand the outcomes when rolling two number cubes (dice).
Each number cube has six faces numbered from 1 to 6. The even numbers on a die are 2, 4, and 6. Therefore, there are 3 even numbers on each die.
Since we are given that the first cube has landed on an even number, this does not change the probabilities for the second cube. The roll of the second cube is independent of the roll of the first cube.
The probability of rolling an even number on a single die is:
\[ P(\text{even}) = \frac{\text{Number of even outcomes}}{\text{Total outcomes}} = \frac{3}{6} = 0.5 \]
Thus, regardless of the outcome of the first cube, the probability that the second cube lands on an even number is still:
\[ P(\text{Second cube is even | First cube is even}) = P(\text{Second cube is even}) = 0.5 \]
Therefore, the correct response is:
0.5