He bought the ducks for 30*10=$<<30*10=300>>300

He sold each duck for 4*5=$<<4*5=20>>20

So he sold all the ducks for 30*20=$<<30*20=600>>600

So he made a profit of 600-300=$<<600-300=300>>300

# Answer

300
<|im_start|>system
You are a helpful assistant.<|im_end|>
<|im_start|>user
John buys 30 ducks for $10 each.  They weigh 4 pounds and he sells them for $5 per pound.  How much profit did he make?
Please reason step by step, and put your final answer within \boxed{{}}.<|im_end|>
<|im_start|>assistant

user
300
John buys 30 ducks for $10 each.  They weigh 4 pounds and he sells them for $5 per pound.  How much profit did he make?
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