Question

Three postal workers can sort a stack of mail 10 minutes , 35 minutes, and 70 minutes respectively. find how long it takes them to sort the mail if all three work together

Answer 1

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Answer:

7 minutes

Explanation:

The total of stacks per minute is ...

1/10 +1/35 +1/70 = (7+2+1)/70 = 1/7 . . . . stacks per minute

The rate in minutes per stack is the reciprocal of this.

Working together, the workers can sort a stack of mail in 7 minutes.