The second rocket goes 500*2=<<500*2=1000>>1000 feet

So the total height is 500+1000=<<500+1000=1500>>1500 feet

# Answer

1500
<|im_start|>system
You are a helpful assistant.<|im_end|>
<|im_start|>user
John builds a model rocket that can travel 500 ft in the air.  He builds a second rocket that can travel twice as high.  What is the combined height of the two rockets?
Please reason step by step, and put your final answer within \boxed{{}}.<|im_end|>
<|im_start|>assistant

user
1500
John builds a model rocket that can travel 500 ft in the air.  He builds a second rocket that can travel twice as high.  What is the combined height of the two rockets?
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