SOLUTION: I'm having the toughest time trying to figure out this Word problem but I can not seem to get it. It takes a computer 8 days to print all of the personal letters for a nationa

Question 147770This question is from textbook Elementary and Intermediate Algebra
: I'm having the toughest time trying to figure out this Word problem but I can not seem to get it.
It takes a computer 8 days to print all of the personal letters for a national sweepstakes. A new computer is purchased that can do the same job in 5 days. How long would it take to do the job with both computers working on it?This question is from textbook Elementary and Intermediate Algebra

Answer by Alan3354(21605) (Show Source):
You can put this solution on YOUR website!
This type is tricky at first. You have to use not the hours per job, but the inverse, or part of job completed per hour. 1 computer takes 8 days, so each day is 1/8 of the job done. The new one does 1/5 of the job each day.
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Add how much they do per day to get the total done per day.
1/8 + 1/5 = 1/Time
5/40 + 8/40 = 1/Time
13/40 = 1/Time
Time = 40/13 days, or 3 days and apx 2 hours.
This looks reasonable as it's less than either working alone but more than 50% of the faster machine alone.