SOLUTION: John Jr. can construct 180 boxes in an hour. John Sr. can only construct 20 boxes in an hour. Working together, how many minutes will it take them to construct 600 boxes?

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Question 916641: John Jr. can construct 180 boxes in an hour. John Sr. can only construct 20 boxes in an hour. Working together, how many minutes will it take them to construct 600 boxes?
Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
Add their rates of working to get
their rate working together
John Jr's rate: ( 180 boxes ) / ( 1 hr )
John Sr's rate: ( 20 boxes ) / ( 1 hr )
--------------------------------
Let +t+ = time in hrs for them to
construct +600+ boxes working
together
-----------------
+180%2F1+%2B+20%2F1+=+600+%2F+t+
Multiply both sides by +t+
+180t+%2B+20t+=+600+
+200t+=+600+
+t+=+3+
+3%2A60+=+180+
It will take them 180 min working together
check:
+180%2F1+%2B+20%2F1+=+600+%2F+3+
+200+=+600%2F3+
+200+=+200+
OK