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### Converting Fahrenheit to Celsius

```
Date: 9/29/95 at 8:47:9
From: Anonymous
Subject: Temperature

Is there a temperature that is the same on both the Celsius and
Fahrenheit scales?
```

```
Date: 9/29/95 at 11:20:0
From: Doctor Ken
Subject: Re: Temperature

Hello!

Nice question.  There's a formula that you can use to get from
Fahrenheit to Celsius: it's

c = (f-32) * 5/9 .

The way we get this formula is to say that when f is 32, c is 0, so
we must have c = (f-32)k, where k is some constant.  To find the
constant, we know that when f = 212 (boiling), c = 100.  So

100 = (212-32)k
100 = 180k
k = 5/9

So with the formula c = (f-32) * 5/9, we can figure out when f = c.
If you want more hints, don't hesitate to write back.

-Doctor Ken,  The Geometry Forum
```

```
Date: 9/29/95 at 17:44:22
From: Doug Zink
Subject: Re: temperature

Dear sir, my question was if there is a temperature that is the
same for both Celsius and Fahrenheit?     Doug
```

```
Date: 9/29/95 at 23:25:43
From: Doctor Ken
Subject: Re: temperature

Hello!

The formula I gave you was one that converted Fahrenheit to
Celsius.  To solve your problem, you'd say "when is f equal to c,"
i.e. solve the equation

x = (x-32) * 5/9.

Does that make sense?

-Doctor Ken,  The Geometry Forum
```

```
Date: 9/30/95 at 1:23:37
From: Doctor Andrew
Subject: Re: temperature

Dr. Ken said:
>So with the formula c = (f-32) * 5/9, we can figure out when f = c.

If there are values of c and f, where f=c, that satisfy that equation,
and that are reasonable temperatures (greater than absolute 0), then
there is such a temperature.  Finding that temperature could be
tough if you don't know much algebra, but we'd be glad to give you
some help.

You could also use your calculator to test different temperatures,
until you get pretty close to the right one (try a value for f and
see if you get the same value as the result of the formula).  There
is a value that is greater than absolute 0 that will work with the
formula.  Can you figure out what it is?

-Doctor Andrew,  The Geometry Forum

```
Associated Topics:
Middle School Temperature

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