Answer: 8 sec
Step-by-step explanation
50 = 1sec
50 + 50 = 100
50 + 50 + 50 + 50 = 200
You keep adding 50 until you reach 400
Every 50 you add is 1 sec so if you add eight 50’s it would be 400 and that would mean it takes him 8 seconds to travel 400ft