SOLUTION: Three postal workers can sort a stack of mail in 10 minutes, 20 minutes, and 60 minutes, respectively. How long will it take all three to sort a stack of mail working together?

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Question 870238: Three postal workers can sort a stack of mail in 10 minutes, 20 minutes, and 60 minutes, respectively. How long will it take all three to sort a stack of mail working together?
Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
Add their rates of sorting
1st workers rate:
( 1 stack ) / ( 10 min )
2nd worker's rate:
( 1 stack ) / ( 20 min )
3rd worker's rate:
( 1 stack ) / ( 60 min )
-------------------------
Let +t+ = the time in minutes
for all three to sort the stack
+1%2F10+%2B+1%2F20+%2B+1%2F60+=+1%2Ft+
Multiply both sides by +60t+
+6t+%2B+3t+%2B+t+=+60+
+10t+=+60+
+t+=+6+
---------------
All three sorting together will take
6 min to sort the stack of mail