Problem:
A manufacturer built a machine which will address envelopes in minutes. He wishes to build another machine so that when both are operating together they will address envelopes in minutes. The equations used to find how many minutes () it would require the second machine to address envelopes alone is:
Answer Choices:
A.
B.
C.
D.
E. none of these answers
Solution:
Since the first machine addresses envelopes in minutes, it addresses envelopes in minute and in minutes. If the second machine addresses envelopes in minutes, then it addresses envelopes in minutes. To determine so that both machines together address envelopes in minutes we use the condition