The first 10 floors are 10*12=<<10*12=120>>120 feet

There are a remaining 20-10=<<20-10=10>>10 stories

They are each 12+3=<<12+3=15>>15 feet

So those stories are 15*10=<<15*10=150>>150 feet

So the total height is 120+150=<<120+150=270>>270 feet

# Answer

270
<|im_start|>system
You are a helpful assistant.<|im_end|>
<|im_start|>user
James builds a 20 story building.  The first 10 stories are each 12 feet tall each.  The remaining floors are each 3 feet taller.  How tall is the building?
Please reason step by step, and put your final answer within \boxed{{}}.<|im_end|>
<|im_start|>assistant

user
270
James builds a 20 story building.  The first 10 stories are each 12 feet tall each.  The remaining floors are each 3 feet taller.  How tall is the building?
train