Final answer:
The peanut butter fudge will fill 4 boxes.
Step-by-step explanation:
To find out how many boxes the peanut butter fudge will fill, we need to calculate 2/3 of the number of boxes the chocolate fudge filled. Since Cathy made enough chocolate fudge to fill 5 boxes, we multiply 5 by 2/3.
Number of boxes the peanut butter fudge will fill = 5 x 2/3 = 10/3 boxes
However, we can't have a fraction of a box, so we need to round the answer to the nearest whole number. Since 10/3 is greater than 3, we round up to 4 boxes.