A machine makes 600 candies a minute. At this rate, how long will it take this machine to make 1800 boxes, each of which contains 24 candies?

1800 boxes with 24 candies each

Total = 1800 * 24 = 43 200 candies

The machine makes 600 candies in 1 minute

1 candy would take (1/600) minute

43 200 candies would take 43200 * 1/600 = 72

= 72 minutes.

Therefore the 1800 boxes would be done in 72 minutes.