A copy machine, working at a constant rate, makes 40 copies per minute. A second copy machine, working at a constant rate, makes 55 copies per minute. Working together at their respective rates, how many copies do the two machines make in half an hour ?
Choose one
A) 90  B) 2,700  C) 4,500  D) 5,400  E) 2,850

Rationale: together the two machines make 40 + 55 = 95 copies per minute . so , in half an hour they will make 95 * 30 = 2,850 copies . answer : e .
Answer: E