Initial height of the tree = 10 feet
Growth rate of the tree per day = 2 feet
Height of the tree on day 1 = 10 feet
Height of the tree on day 2 = 10 + 2 = 12 feet
Height of the tree on day 3 = 12 + 2 = 14 feet
Height of the tree on day 4 = 14 + 2 = 16 feet
Height of the tree on day 5 = 16 + 2 = 18 feet
Height difference of the tree between day 5 and day 1 = 18 − 10 = 8 feet
Therefore, 8 feet is the difference between the heights of the tree on the 1st day and 5th day.