SOLUTION: Three postal workers can sort a stack of mail in 30 ​minutes, 30 ​minutes, and 60 ​minutes, respectively. Find how long it takes them to sort the mail if all thre

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Question 1127387: Three postal workers can sort a stack of mail in 30 ​minutes, 30 ​minutes, and 60 ​minutes, respectively. Find how long it takes them to sort the mail if all three work together.
Answer by addingup(3677) About Me  (Show Source):
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To find out how quckly they can do it as a team, first we have to bring their individual results down to a common metric so that we can compare apples with apples. So let's first bring their rates to one stack:
:
Worker 1: 1/30 (one stack/30 minutes)
Worker 2: 1/30
Worker 3: 1/60
1/30 + 1/30 + 1/60 = 1/minute
multiply all times 60:
2t + 2t + 1t = 60
5t = 60
t = 12 minutes. This is how long it will take the three working together.