Boiling Water Temp: Celsius vs. Fahrenheit

[Foehammer]

Homework Statement

A Celsius and a Fahrenheit thermometer are dipped in boiling water. The temperature of the water is brought down until the Fahrenheit thermometer reads 140°. So, the fall in temperature registered by Celsius scale is:
30
40
50
80

Homework Equations

F=(C*(9/5))+32
C=(F-32)*(5/9)

The Attempt at a Solution

Boiling water is 212 F. 212-140=72.
Convert 72 F to C and I get 22.223 C.
My answer doesn't match any of the choices.

 

[rock.freak667]

If F=1.8C+32

Then F1=1.8C1+32
and F2=1.8C2+32

So you change in F, F2-F1= ? (write in terms of the formula and you'll see that the change in F can't be converted to C using the standard formula).

Alternatively, convert everything to C first.

 

[Foehammer]

If F=1.8C+32

Then F1=1.8C1+32
and F2=1.8C2+32

So you change in F, F2-F1= ? (write in terms of the formula and you'll see that the change in F can't be converted to C using the standard formula).

Alternatively, convert everything to C first.

Got it. Thanks a lot!

 

[SteamKing]

Homework Statement

A Celsius and a Fahrenheit thermometer are dipped in boiling water. The temperature of the water is brought down until the Fahrenheit thermometer reads 140°. So, the fall in temperature registered by Celsius scale is:
30
40
50
80

Homework Equations

F=(C*(9/5))+32
C=(F-32)*(5/9)

The Attempt at a Solution

Boiling water is 212 F. 212-140=72.
Convert 72 F to C and I get 22.223 C.
My answer doesn't match any of the choices.

The reason '32' appears in these temperature conversion formulas is that in the Celsius scale, water freezes at 0 C, while this occurs at 32 F on the Fahrenheit scale. Between freezing and boiling, there are 180 Fahrenheit degrees and 100 Celsius degrees, so each Celsius degree is 180/100, or 9/5 Fahrenheit degrees.

 

[HalfLostAndSearching]

Based on your calculations, the correct answer would be 40. The fall in temperature registered by the Celsius scale is 40 degrees, which can be found by subtracting the initial temperature of 212 degrees Fahrenheit from the final temperature of 22.223 degrees Celsius. This conversion can also be verified by using the equation C=(F-32)*(5/9), where C is the temperature in Celsius and F is the temperature in Fahrenheit. Therefore, the correct answer is 40.