Question 450613
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Hi,
"Erica could do 10 math problems in 20 minutes OR 10/20 = .5 in 1 min
Penny could do 15 math problems in 25 minutes OR 15/25 = .6 in  1 min
If they worked together... 
how many minutes would it take Erica and Penny to do 30 math problems?"
Let x represent the amount of minutes
 .5x + .6x = 30
       1.1x = 30
          x = 30/1.1 =  27.2727 minutes