Answer: The total number of machines needed is 24.
Step-by-step explanation: Each machine can process 40 envelopes in 8 minutes.
We need to determine how many machines are necessary to achieve a rate of 120 envelopes per minute.
The UNITARY method will be employed to find the solution.
In 8 minutes, a machine processes 40 envelopes.
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This indicates that for stamping 5 envelopes in a minute, one machine is sufficient.
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Consequently, the quantity of machines required to stamp 120 envelopes per minute is found using:

Thus, a total of 24 machines will be necessary.
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