Reasoning and answer: 2.5 * 5 = 12.5 hours. 0.5 * 3 = 1.5 hours. 12.5 + 1.5 hours = 14 hours. 14 hours = 14 * 60 = 840 minutes. It would take 840 minutes to groom 5 dogs and 3 cats.
The answer: 840
What was the question?
Question: It takes 2.5 hours to groom a dog and 0.5 hours to groom a cat. What is the number of minutes it takes to groom 5 dogs and 3 cats?

Reasoning and answer: First find the total time Ellen spends painting lilies: 5 minutes / lily * 17 lilies = 85 minutes. Then find the total time Ellen spends painting roses: 7 minutes / lily * 10 roses = 70 minutes. Then find the total time Ellen spends painting orchids: 3 minutes / orchid * 6 orchids = 18 minutes. Then find the total time Ellen spends painting vines: 2 minutes / lily * 20 vines = 40 minutes. Then add the amount of time Ellen spends on each type of flower to find the total time: 85 minutes + 70 minutes + 18 minutes + 40 minutes = 213 minutes.
The answer: 213
What was the question?
Question: Ellen is painting flowers on a vase. It takes her 5 minutes to paint a lily, 7 minutes to paint a rose, 3 minutes to paint an orchid, and 2 minutes to paint a vine. How long will it take her to paint 17 lilies, 10 roses, 6 orchids and 20 vines?

Reasoning and answer: At least one person lives in 85 / 100 * 120 = 102 apartments. At least two persons live in 60 / 100 * 120 = 72 apartments. So in every of the 102 - 72 = 30 apartments, only one person is living.
The answer: 30
What was the question?
Question:

Show your work and conclude with the exact phrasing "Therefore, the final answer is [answer]." where [answer] is just the final number or expression that solves the problem.
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In a block of flats, there are 120 apartments. 85% of them have at least 1 resident, while 60% of the apartments have at least two residents. How many apartments have only one resident?