GRE Practice Question Incorrect?

Question

This is a sample GRE question. The answer claims that we cannot make an inference due to insufficient information. *Compare the following quantities:* Of the 25 people in Fran’s apartment building, there are 9 residents who use the roof only for tanning and 8 residents who use the roof only for gardening. The roof is only used by tanners and gardeners. **Quantity A:** The ratio of people who use the roof to total residents **Quantity B:** 17:25 In this question, we do not know if there is any overlap between tanners and gardeners. How many, if any, residents do both activities? Since we don’t know, the relationship cannot be determined from the information given. Given that this question specifies **only**, how can the answer imply that there may be an overlap? E.g. If I use the roof for tanning *and* gardening then I do **not** use the the roof *only* for tanning. Thoughts?

Answer 1

Hope this helps!

Answer 2

9:8

You're correct; they need to be more specific by using names.