Dave started hiking at 120 feet below sea level.

a) If he climbed 750 feet, whats his elevation now?

b) Dave then descended 420 feet in 1 hour. Find the average change in elevation per minute.

c) Dave started his descent at 4 p. m. Use the rate in B) to determine the time he reaches sea level.

A) 750-120=630 ft. His elevation is 630 ft. above sea level now. b) 420 ft/hour. 60 minutes=1 hour. 420 ft/60=7 ft/minute. The average change in elevation is 7 ft/minute. c) 630ft/7ft=90 minutes. If he starts at 630 ft and descends at a speed of 7 ft/min, it will take him 90 minutes. 90 minutes=1 1/2 hours. 1 1/2 h+4 h=5 1/2 hours. If he's starts his descent at 4 pm, he will reach sea level at 5:30 p. m.