{
  "hints": [
    "Use the average speed to find the total time. Total time = Total distance / Average speed.",
    "Total distance = 1000 m. Total time = 1000 / 1 = 1000 s. Running took 600 / 3 = 200 s.",
    "Walking time = 1000 - 200 = 800 s. Walking speed = 400 / 800 = 0.5 m/s."
  ]
}