A worker at a snack stand opened a new box of cups. On the first day, the worker used 30 cups from the box. On the second day, the worker used 15% of the remaining cups in the box. A total of 90 cups were used on the second day. What was the original number of cups in the box before any cups were used?

630 cups

Step-by-step explanation:

Percentages

This problem is most easily solved backward, i.e., from the final data up to the beginning.

There was a new box of cups and the worker at a snack stand opened it. He first used 30 cups from the box and the second day he uses 15% of the remaining cups in the box, and we are told that represents 90 cups.

If 15% (0.15) equals 90 cups, then the number of cups before the second day was 90/0.15 = 600 cups.

On the first day, we used 30 cups, thus the original number of cups in the box was 600+30=630 cups