Answer: it would take them 40/13 hours
Step-by-step explanation:
If Naomi were to paint her living room alone, it would take 5 hours. it means that the rate at which she paint her living room alone is 1/5
Her sister Jackie could do the job in 8 hours. it means that the rate at which Jackie paint the living room is 1/8
If they work together, they would work simultaneously and their individual rates are additive. This means that their combined working rate would be
1/5 + 1/8 = (8 + 5)/40 = 13/40
Assuming it takes t hours for both of them to clean the room working together, the working rate per hour would be 1/t. Therefore,
13/40 = 1/t
t = 40/13 hours
