Mary can clean her apartment in 6 hours, while her roommate can clean the apartment in 5 hours. If they work together,
how long would it take them to clean the apartment?
Round your answer up to the nearest minute.
Provide your answer below:

The weight of a radioactive isotope was 96 grams at the start of an experiment. after one hour, the weight of the isotope was half of its initial weight. after two hours, the weight of the isotope was half of its weight the previous hour. if this pattern continues, which of the following graphs represents the weight of the radioactive isotope over time? a. graph w b. graph x c. graph y d. graph z