If 80 persons can perform a piece of work in 16 days of 10 hours each, how many men will perform a piece of work twice as great in tenth part of the time
working 8 hours a day supposing that three of the second set can do as much
work as four of the first set?

The number of men needed to perform a piece of work twice as great in tenth part of the time  working 8 hours a day supposing that three of the second set can do as much  work as four of the first set is:

Step-by-step explanation:

To find the answer, first, we're gonna find how many hours take to make the piece of work in 16 days, taking into account each day just has 10 hours:

Now, we divide the total hours among the number of persons:

This equivalence isn't the real work of each person, we only need this value to make the next calculations. Now, we have a piece of work twice as great as the first, then, we can calculate the hours the piece of work needs to perform it (twice!):

We need to make this work in tenth part of the time working 8 hours a day, it means:

Now, we know three of the second set can do as much  work as four of the first set, taking into account the calculated equivalence, we have:

So, three persons of the second set can make a equivalence of 8 hours. At last, we calculate all the number of workers we need in a regular time:

Remember we need to perform the job not in a regular time, we need to perform it in tenth part of the time, by this reason, we need 10 times the number of people:

With this calculations, you can find the number of men needed to perform a piece of work twice as great in tenth part of the time  working 8 hours a day supposing that three of the second set can do as much  work as four of the first set is 1200 persons.

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step-by-step explanation: