After an hour (4pm to 5pm) the temperature drops 18e⁻⁰˙⁶=9.9℉, so the temperature after an hour will be 68-9.9=58.1℉.
(The change -18e⁻⁰˙⁶ is negative indicating a drop in temperature.)
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first 3 nines have the greater value but the first one has the highest and the least one is the last nine.
Let the time that you caught up with your friend be t, then
8.5 - 3.4t = 8 - 3t
3.4t - 3t = 8.5 - 8
0.4t = 0.5
t = 0.5/0.4 = 1.25
therefore, you will catch up with your friend after 1.25 hours.
b.) time it will take you to cross the finnish line = 8.5/3.4 = 2.5 hours
After 2.5 hours, distance covered by your friend = 3 x 2.5 = 7.5 miles
Therefore, when you cross the finish line, you are 8 - 7.5 = 0.5 miles ahead of your friend.