If I roll a die, what is the chance I'll roll a number less than 4?

When rolling a fair six-sided die, the numbers that are less than 4 are 1, 2, and 3. Since each number has an equal chance of landing face up, there are 3 favorable outcomes out of the total 6 possible outcomes.

Using the probability formula:

[ \text{Probability} = \frac{\text{Number of favorable outcomes}}{\text{Total number of possible outcomes}} ]

We can calculate the probability:

[ \text{Probability} = \frac{3}{6} = \frac{1}{2} ]

So, the chance of rolling a number less than 4 on a fair six-sided die is 50%.