Final answer:
To find the number of vacation days used by Charles, simply multiply 2 (the total vacation days) by the fraction of the vacation time he decides to use.
Step-by-step explanation:
The question asks us to calculate the portion of vacation time that Charles uses, given that he has earned 2 days of vacation time. To find out how many days he uses when he takes a fraction of his 2-day vacation, we multiply the number of vacation days (2) by the fraction representing the portion he uses. For instance, if Charles uses one half of his vacation time, we would calculate 1/2 of 2 days, which equals 1 day. Thus, Charles would be using 1 day of vacation.