If 10 hens lay 80 eggs, then 1 hen lays 80 / 10 = <<80/10=8>>8 eggs in 10 days.

That means one hen is laying 8 / 2 = <<8/2=4>>4 eggs in 5 days.

So in 15 days, 1 hen will lay 3 times more eggs, so 4 * 3 = 12 eggs.

All hens in total will then lay 25 * 12 = <<25*12=300>>300 eggs in 15 days.

# Answer

300
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Martin owns a farm with hens. 10 hens do lay 80 eggs in 10 days. Martin decided to buy 15 more hens. How many eggs will all hens lay in 15 days?
Please reason step by step, and put your final answer within \boxed{{}}.<|im_end|>
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300
Martin owns a farm with hens. 10 hens do lay 80 eggs in 10 days. Martin decided to buy 15 more hens. How many eggs will all hens lay in 15 days?
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