SOLUTION: Selma�s class is making care packages to give to victims of a natural disaster. Selma packs one box in 5 minutes and has already packed 12 boxes. Her friend Trudy packs one box in

Question 1122402: Selma�s class is making care packages to give to victims of a natural disaster. Selma packs one box in 5 minutes and has already packed 12 boxes. Her friend Trudy packs one box in 7 minutes and has already packed 18 boxes. How many more minutes does each need to work in order to have packed the same number of boxes?
Answer by ikleyn(52810) (Show Source): You can put this solution on YOUR website!
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Selma      Trudy

12 + x/5 = 18 + x/7    (x = amount of time, in minutes)


x/5 - x/7 = 18 - 12


 -  = 6


 = 6  ====>  x =  = 105 minutes.


Answer.  105 minutes,  or 1 hour and 45 minutes.

Another solution using fingers

Every 35 minutes Selma packs 7 boxes, while Trudy packs 5 boxes.

Thus every 35 minutes Selma decreases the difference between them in 2 boxes.


Since the original difference was 6 boxes, Selma needs 3 times 35 minutes, or 105 minutes, in all, to catch Trudy.

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