If the hiker covers 700 feet every 30 minutes. In an hours time the hiker is 1400 feet relative to the peak of the mountain. 30 minutes later which is actually 1 hrs 30 minutes later the hiker is 1400 + 700 = 2100 feet relative to the peak of the mountain. In another 30 minutes time (now 2 hours later) the hiker is 2100 + 700 = 2800 feet relative to the mountain peak. 30 minutes later (now 2hr 30 minutes) hiker is 2800 + 70. = 3500 feet and so in 3hrs time the hiker is 3500 + 700 = 4200 feet relative to the peak of the mountain.