One copy machine can make 15 copies a minute, and a second copy machine makes 10 copies a minute. If the two copiers work together, how long would it take them to make 1,000 copies?
Choose one:
A) 20 minutes
B) 30 minutes
C) 40 minutes
D) 50 minutes
E) 60 minutes

Rationale: total work done by both machines in a minute = 15 + 10 = 25 copies total number of copies required = 1000 time = 1000 / 25 = 40 mins answer c
Answer: C