SOLUTION: Arman can finish repairing the roof in three hours. If Armando helps his father Arman, the job will be done in two hours. If Armando decides to work alone, how long would it take h

Algebra ->  Rate-of-work-word-problems -> SOLUTION: Arman can finish repairing the roof in three hours. If Armando helps his father Arman, the job will be done in two hours. If Armando decides to work alone, how long would it take h      Log On


   

Question 1168723: Arman can finish repairing the roof in three hours. If Armando helps his father Arman, the job will be done in two hours. If Armando decides to work alone, how long would it take him to finish repairing the roof?

Answer by josgarithmetic(39625) About Me  (Show Source):
You can put this solution on YOUR website!
1%2F3%2B1%2Fy=1%2F2

1%2Fy=1%2F2-1%2F3
6=3y-2y
highlight%286=y%29---------------Armando, needs 6 hours if working alone.


Just to see more clearly:
Arman, the father, work rate 1%2F3
Armando, the son, work rate 1%2Fy
Both working together, work rate 1%2F2
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Question asks what is the time needed for Armando, the son, the do 1 job by himself?

The rates are additive for working together, so 1%2F3%2B1%2Fy=1%2F2.