The distance to the destination is 4 hours * 50 miles/hour = <<4*50=200>>200 miles.

Traveling at 100 miles per hour, it will take 200 miles / (100 miles/hour) = <<200/(100)=2>>2 hours.

# Answer

2
<|im_start|>system
You are a helpful assistant.<|im_end|>
<|im_start|>user
A train takes 4 hours to reach a destination at a speed of 50 miles per hour. How long would it take if it traveled at 100 miles per hour instead?
Please reason step by step, and put your final answer within \boxed{{}}.<|im_end|>
<|im_start|>assistant

user
2
A train takes 4 hours to reach a destination at a speed of 50 miles per hour. How long would it take if it traveled at 100 miles per hour instead?
train