Temp celsiius to Farenheit question

  Terry Brown 19:42 23 Sep 2010

At a local quiz night, the question come up
'What is 50 celsius in the farenheit scale..

I thought 100 c & 212 f are boiling point of water, therefore half of 100=50 and half of 212 =106.
The answer is 106f

Wrong-- The answer is 122f.

Can anyone explain why?

  bri-an 19:52 23 Sep 2010

F = (9/5 *C) +32

  muddypaws 19:53 23 Sep 2010

No! But you can experiment here click here

  morddwyd 19:54 23 Sep 2010

Because the conversion is non-linear.

At some temperature, I can't remember which, the temperatures on both scales are equal, so using your method they should be equal all the way up, and down.

  canarieslover 19:58 23 Sep 2010

Celcius freezing point is at 0 degrees and Farenheit freezing point is at 32 degrees therefore you should have minused 32 degrees from 212 before halving it and then added the 32 back onto the result.

  rdave13 19:58 23 Sep 2010
  bri-an 20:01 23 Sep 2010

Freezing to boiling on F scale is 32 to 212 = 180 'degrees'
Same on C scale is 0 to 100, ie 100 degrees
Thus 180 deg F is equiv to 100 degC.
Ratio is 180/100 which is 9/5.

Bur F scale starts at 32 degrees (freezing that is), so 32 must be added to get the correct conversion.

  BT 08:20 24 Sep 2010

According to rdave's picture its -40C = -40F

  bri-an 08:35 24 Sep 2010

Using the formula I gave at the start, if X is the same temp on each scale then

X = 9/5*X +32
Multiply both side of equation by 5 and get

5X = 9X +160
5X - 9X =160
-4X = 160
X = -40

So -40 must be the 'equal' temps you need.

  Quickbeam 09:14 24 Sep 2010

The double it and add 30 way is a quick, but rough mental calculation that's only OK in a limited rage of common weather temperatures. When the Met office was changing from Farenheight to Celcius they used to quote it for our quick conversion reference.

  skeletal 10:03 24 Sep 2010

The other interesting thing about the quiz question is they gave a small clue to the solution in the question itself. The number 50 is one of the easiest to work out in your head, because you have to divide by 5 first, the answer ten is then easy to use to multiply the 9.

For these quiz types problems, I always look for such clues. If you need Excel to work it out, chances are you are on the wrong path.

It does help if you know the formula though!


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