Below is an instruction that describes a task. Write a response that appropriately completes the request in English. Please answer in English.

### Instruction:
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?

### Response:
The second rocket goes 500*2=<<500*2=1000>>1000 feet
So the total height is 1000+500=<<1000+500=1500>>1500 feet
#### 1500