Final answer:
It takes 7.5 minutes for Christy and Rabia to eat one cup of popcorn, calculated by dividing the total eating time by the number of cups consumed.
Step-by-step explanation:
Christy and Rabia eat 4 cups of popcorn in 30 minutes. To find out how many minutes it takes for them to eat one cup of popcorn, we simply divide the total minutes by the number of cups.
30 minutes ÷ 4 cups = 7.5 minutes per cup.
Therefore, it takes 7.5 minutes for Christy and Rabia to eat one cup of popcorn.