Question

2. The temperature in Indianapolis, Indiana, at 5:00 A.M. was 15 °F. If the temperature drops 2 degrees each hour, what is the temperature in degrees Fahrenheit at 2:00 PM? A. 17°F B. -17°F C. -14°F D. 32°F

Answer 1

The initial temperature is 15ºF

Each passig hour the temperature drops 2 degrees Celcius

First pass the initial temperature from Fahrenheit to Celcius

`\begin{gathered} ºC\cdot(9)/(5)+32=ºF \\ (ºF-32)\cdot(5)/(9)=ºC \\ (15-32)\cdot(5)/(9)=-9.44ºC \\ \end{gathered}`

The initial temperature is -9.44ºC and the drop is 2ºC per hour (x represent the number of hours), the time lapse is 9 hours

You can calculate the final temperature as

`\begin{gathered} T=-9.44-2x \\ T=-9.44-2\cdot9 \\ T=-27.44ºC \end{gathered}`

Next pass the temperature back to Fahrenheit using the first formula:

`\begin{gathered} (ºC\cdot(9)/(5))+32=ºF \\ (-27.44\cdot(9)/(5))+32=-17.392ºF \end{gathered}`

The final temperature is -17.392ºF, aprox -17ºF

Correct choice is B.