A factory produces nuts and bolts. A machine in it produces only nuts

Given: A factory produces nuts and bolts. A machine in it produces only nuts while another produces only bolts. The machine producing only nuts produces 400 nuts per minute and need to be cleared for 15 minutes after production of 2000 nuts. The machine producing only bolts produces 300 bolts per minute and needs to be cleared for 15 minutes after production of 3000 bolts.
Asked: Find the minimum time required to produce 12000 pairs of bolts and nuts if both machines are operated simultaneously.

Time required by machine A to produce 2000 nuts = 5 mins + 15 mins rest
Time required by machine B to produce 3000 bolts = 10 mins + 15 mins rest

Time required by machine A to produce 12000 nuts = 5 + 15 + 5 + 15 + 5 + 15 + 5 + 15 + 5 + 15 + 5 = 30 + 75 = 105 mins
Time required by machine B to produce 12000 bolts = 10 + 15 + 10 + 15 + 10 + 15 + 10 = 40 + 45 = 85 mins

The minimum time required to produce 12000 pairs of bolts and nuts if both machines are operated simultaneously = max(105,85) = 105 mins


IMO C

Hello from the GMAT Club BumpBot!

Thanks to another GMAT Club member, I have just discovered this valuable topic, yet it had no discussion for over a year. I am now bumping it up - doing my job. I think you may find it valuable (esp those replies with Kudos).

Want to see all other topics I dig out? Follow me (click follow button on profile). You will receive a summary of all topics I bump in your profile area as well as via email.