Elmer has a pond that initially contained 2400 pollywogs, but these pollywogs matured into toads and left the pond at a constant rate of 50 pollywogs per day.  In addition, Elmer has a son named Melvin, who loves to catch pollywogs, remove them from the pond, and release them into a nearby stream.  For the first 20 days, Melvin caught 10 pollywogs per day and released them into the stream.  How many days did it take for all of the pollywogs to disappear from the pond?
For the first 20 days, the combined rate of disappearance of pollywogs from the pond is 50+10=<<50+10=60>>60 pollywogs per day.
During these first 20 days, the total number of pollywogs removed was 60*20=<<60*20=1200>>1200 pollywogs.
This means after 20 days there were 2400-1200=<<2400-1200=1200>>1200 pollywogs left in the pond.
At a disappearance rate of rate 50 pollywogs per day, it will take an additional 1200/50=<<1200/50=24>>24 days for the rest of the pollywogs to disappear from the pond.
Thus, overall, it will take 20+24=<<20+24=44>>44 days for all of the pollywogs to disappear from the pond.
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