working together Alberto and Amanda can paint a fence in 4.12 hours. had she done it alone it would have taken Amanda 10 hours. find how long it would take Alberto to do it alone. A) 6.75 B) 5.02 c) 7.54 D)7.01

  D)  7.01

Step-by-step explanation:

The rates of doing work, in terms of jobs per hour, will add when the two painters are working together. If A represents Alberto's time to do the job alone, we have ...

  1/4.12 = 1/10 + 1/A

(Jobs per hour is the inverse of hours per job.)

  A = 1/(1/4.12 -1/10) ≈ 7.0068 ≈ 7.01

It takes Alberto 7.01 hours to do the job alone.