### Instruction: We have a cube with 4 blue faces and 2 red faces.  What's the probability that when it is rolled, a blue face will be facing up?### Response: This is a problem about probability, which is the ratio of favorable outcomes to possible outcomes.
In this case, the possible outcomes are the six faces of the cube, and the favorable outcomes are the four blue faces.
So the probability is 4/6, which can be simplified by dividing both numerator and denominator by 2.
The simplified probability is 2/3.