What is the probability of spinning a number less than 6 or rolling a number less than 6?

There are 6 possible outcomes {1,2,3,4,5,6} that you could get from a 6-sided die.

Of these, {1,2,3} are less than 4 i.e. there are 3 outcomes that satisfy the requirement out of 6.

Thus, the probability that you get a number less than 4 on rolling a 6-sided die once would be 3/6 = 1/2