Jack accepted a job to paint a new house. he calculated that he can complete the job in 30 hours. he hired a trainee to assist him. he has seen the trainee work and estimates that it the trainee working alone would take 45 hours to complete the job. how much time should the two of them working together need to paint the house? (round your answer to the nearest tenth.)

20hours

Step-by-step explanation:

Jack can complete the painting in 30hours. The fraction he can paint per hour is thus 1/30

Trainee can complete the painting in 45hours, the fraction he can paint per hour is 1/45

If they are working together, the fraction that can paint in an hour is :

1/45 + 1/30 = 5/90 = 1/18

Now we know they can paint 1/18 of the room in an hour, the number of hours needed to completely paint the room is thus 1/1/18 = 18 hours

Rounding up answer to the nearest tenth is 20hours