Question

one winter night the temperature fell 15 degrees between midnight and 5 a.m. By 9 a.m. the temperature had doubled from what it was at 5 a.m. .By noon, it had risen another 10 degrees to 32 degrees. what was the temperature at midnight?

Answer 1

Let's call the temp at midnight "x," and take this problem one piece of information at a time.

"the temperature fell 15 degrees fahrenheit between midnight and 5 am."

temp at 5am = (x - 15)

"By 9 am the temperature had doubled from what it was at 5am."

temp at 9am = 2(x -15) = 2x - 30

"By noon, it had risen another 10 degrees to 32 degress fahrenheit"

32 = 2x - 30 + 10

32 = 2x - 20

52 = 2x

26 = x

PROOF:

5am : 26 - 15 = 11

9am : 11 * 2 = 22

noon: 22 + 10 = 32