Solution: suppose there are x people who arrange the sorting first. At the same time, let the total workload be 1.
It takes 30 hours for a person to do it alone, so a person's work efficiency is 1/30.
Arrange some people to spend 1 hour finishing first, then the completed workload is: x× 1/30× 1=x/30.
Then six people were added, and the number of people sorted out at this time was (x+6).
They worked together for two hours, and the amount of work completed was (x+6 )×1/30× 2 = (x+6)/15.
At this time, the task has just been completed: x×1/30×1+(x+6 )×1/30× 2 =1.
Solve this equation and get: x=6.
A: There are six people who arrange the sorting first.
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The solution you gave is understood as follows.
The person who arranged it first actually worked for three hours.
Their workload for three hours is: x× 1/30×3.
Then the six people who joined have been working for 2 hours.
Their two-hour workload is: 6× 1/30×2.
Their total workload is 1, so it is: x x1/30 x 3+6 x1/30 x 2 =1.
Solve this equation and get: x=6.
A: There are six people who arrange the sorting first.