First find his current travel time 600 miles / 50 miles per hour = <<600/50=12>>12 hours.

12 hours - 4 hours = <<12-4=8>>8 hours desired travel time

600 miles / 8 hours = <<600/8=75>>75 miles per hour.

75 miles per hour - 50 miles per hour = <<75-50=25>>25 miles per hour faster

# Answer

25
<|im_start|>system
You are a helpful assistant.<|im_end|>
<|im_start|>user
Kevin is taking a 600-mile trip, traveling at a rate of 50 miles per hour. How much faster must he travel to decrease his travel time by 4 hours?
Please reason step by step, and put your final answer within \boxed{{}}.<|im_end|>
<|im_start|>assistant

user
25
Kevin is taking a 600-mile trip, traveling at a rate of 50 miles per hour. How much faster must he travel to decrease his travel time by 4 hours?
train