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# A Little Trick for Converting Centigrade to Fahrenheit

Nov 12th, 2009, 09:29 AM
#21

Join Date: Apr 2005
Posts: 5,215
So the 180/100, 9/5, is the scale conversion factor and the 32 is because F scale starts freezing at 32.

Having a BS in physics and engineering I learned the cgs/metric years ago and wished the USA had followed thru on our half hearted attempt to convert in 1975(?). I know believe we will and are, just going very slowly.

regards - tom
Nov 12th, 2009, 10:21 AM
#22
Original Poster

Join Date: Jan 2009
Posts: 770
Sandi, jczinn - read no further

Celia, according to an article in USAToday, "The Celsius temperature scale is still sometimes referred to as the "centigrade" scale. Centigrade means "consisting of or divided into 100 degrees." The Swedish Astronomer Andres Celsius (1701-1744) developed the centigrade scales for scientific purposes. It has 100 degrees between the freezing point (0°C) and boiling point (100°C) of pure water at sea-level air pressure. An international conference on weights and measures voted to name the centigrade scale after its inventor in 1948." In addition an article in Science said that at the international conference in 1960 the scale was defined in a way that makes the adjective centigrade inexact.

And---but I'll need Rizzuto and Tom to weigh in/confirm this---your approach of taking 10% of the doubled Celsius temp is more than just close enough: it gives you exactly F = 9/5C + 32 !

Best, Steve
Nov 12th, 2009, 10:30 AM
#23

Join Date: Jan 2003
Posts: 5,997
You're exactly right, Steve. Celia's method of doubling the Celsius/Centigrade temp, subtracting 10%, then adding 32 is another way of calculating (expressing) the F = (9/5)C + 32 formula.
Nov 12th, 2009, 11:32 AM
#24

Join Date: Feb 2004
Posts: 3,237
>>>Metric is so easy; everything divides by 10 or 100.

>>>How many inches in a foot? How many feet in a yard? What the he...ll!!!

>>>Percy, what's there not to get used to?

Safarimama - it's not the math that takes getting used to. It's having a sense for the meaning. I know how 70 degrees F feels because I've grown up knowing. I know I need a jacket for 50 and a winter coat for 30. And if it's 80, short sleeves are perfect. But 20C? It's meaningless to me. Ditto for feet and miles. I know how long it takes to walk a mile or drive 10 miles. I don't have the same feel for kilometers - I have to do the conversion .6 conversion in my head. It's the "feel" for temperature and distance that is hard to adjust to. I think it must be like learning a new language - beginners can look up words and translate. But you have to practice a long time to get to where you can actually think in the new language. Hope that explains it
Nov 12th, 2009, 11:53 AM
#25

Join Date: Feb 2003
Posts: 13,216
well safarimama,

When you were totally used to miles feet and pounds and then you get the metric system, you only think it is mentally easy !~

let me give you some examples

1.If some asks me to raise my hand to a level of 5 feet , 7 inches... I can come pretty close.

Tell me to raise my hand to a level of 142 cm ....I would only be guessing ,as I try mentally to convert to feet and inches.

2.2 pounds = 1 Kilogram, so when you go shopping you buy meat that is \$4.20 per Kilogram (is that a good deal)

I am happy to see Tiger Woods hit the ball 325 Yards, I do not want an announcer telling me Woods just hit the ball 296.95 meters.!!!

We had a big rain storm !!! it rained 38 millimeters !!!, now spread your thumb and index finger to 38 millimeters !!...not easy is it.!!

Now 38 millimeters is 1 and a half inches! ( okay ,okay it is 1.496063 inches to be more exact.

If you can easily know just how high 117 centimeters is

and that a football player just just made a 17.2 meter catch.....you way ahead of me

Oh yes,I majored in Math and Physics, so I do know all about the mertic systems.

I can remember having to calculate Forces in Pounds and then converting that into Newtons...or dynes

I can tell you that I would rather some tell me that the pressure is 10 pounds per square inch....then to tell me that the
pressure is 68,960 Newtons per square meter.!!!

Your better than I am by a mile if you can handle the metric system, if you come from a non-metric country !!!
Nov 12th, 2009, 11:59 AM
#26

Join Date: Feb 2003
Posts: 13,216
althom 1122

You are Right on , I could not have said it better.

I have no feel for 37 Kilometers but I do for 37 miles.

If if sterak is \$7.00 /pound , I have a feel for that.

If steak is \$14.30/ Kilogram , I do not want if that is a good deal.

When the weather man tells me it rained 8 inches over the past 2 days and floods are everywhere.....I can feel that.

If he said is rained 78 millimeters.??? what is that !!

Thanks for saying what I wanted to say, in a better way than I could have !
Nov 12th, 2009, 12:13 PM
#27

Join Date: Mar 2007
Posts: 8,675
Percy - well said.

I'll stick with what I know and the few things I've figured out to get thru metric environments.

Anyone who grew up in the 70s, knows that a Kg is 2.2/lbs.

For Kilometers, I just subtract 1/3rd and know my distance or speed.

And, 3.5/ltrs = 1/gallon.

When it comes to temperature, I know cold, hot or warm... the exact degrees - who cares.

I can go about doing most anything to get me thru and not break the law!!!
Nov 12th, 2009, 12:21 PM
#28

Join Date: Aug 2006
Posts: 641
OK, I stand corrected; I was only thinking of how easy the metric system and Celcius is to figure.

Being born and growing up in Sweden, the land of Celcius, living in the US for the past 20 plus years now, I have a "feel" for both Celcius and Farenheit. That wasn't as difficult to aquire as you make it sound. Just give it a year and you'll be a convert.

However, but to be honest, I still don't know how many inches in a foot, how many feet in a yard or ounces in pound etc. That makes totally no sense at all to me. I never got a feel for that. It's just totally impossible to remember.

I also miss the 24 hour clock!!!
Nov 12th, 2009, 12:27 PM
#29

Join Date: Mar 2007
Posts: 8,675
Recall when my brother first moved to Canada, the first snowstorm when the weather person said their were XXXcm of snow... he had to ask his students how much that was. To him anything that didn't inhibit his driving was perfectly okay, whether inches or cm. And, after 25/yrs up north, he's just getting the hang of it... and to think that he teaches math. Poor kids! Ha! Ha!
Nov 12th, 2009, 06:28 PM
#30

Join Date: Feb 2003
Posts: 13,216
Hi sandi and Hi safarimama :

Well you would think that if a person grew up with the metric system, then pounds and inches and feet and miles would be foreign to them !!?

Not so!

Canada converted to metric in the early 1970's and people still do not like it.

The government tried to force it upon everyone quickly by having "Metric Police" going around making sure that grocery stores and public places were using metric.

My nephew was born the early 1980's and he took metric in school....had to ,there was no choice.

But to this day when he asks me about distance he used miles.

He would not ask me , for example, how many Kilometers from Los Angeles to Palm Springs, but rather how many MILES is it .

In fact, if I think about it , not one of my Canadian friends has ever talked to me in metric, no matter how old he is !

In my humble opinion they should have used metric for science when neeed,or for international trade when need, but left pound/yards/miles alone.

Oh yes, Canada thought their trade would boom internationally when they converted to metric....

A government study later on proved that was not the case.

I am very pleased that the USA has not gone metric !!

Good Night ladies. ( bedtime sandi )
Nov 12th, 2009, 07:18 PM
#31

Join Date: Feb 2003
Posts: 13,216
Oh yes I forgot to mention it safarimama!,but I LOVED Stockholm.

What a gorgeous place to visit and walk around.

The views from the City Hall Tower back onto Gamla Stan are just terrific.

Okay now for sure Good Night Ladies ( sshhh sandi is sleeping already) .
Nov 12th, 2009, 07:25 PM
#32

Join Date: Aug 2006
Posts: 641
Miles!????!!! Oh yes!!! Don't know anything about growing up in Canada, but .... One Swedish mile is 10KM!!!

What are you talking about? I consider one mile to be just that -- 10km. I have no idea how many yards is in an English mile? Do you or anybody?

Does it mean anything?

I drive a Volvo, so when in Canada (to visit LyndaS), it's easy to compare. 100KM is 60 miles (American). It's on my speedometer!!! Easy enough for me. I'm blond (or used to be). I get a "feel" for it then. Just don't ask me to convert it, pleeeeeease!
Nov 13th, 2009, 02:27 AM
#33

Join Date: Jan 2003
Posts: 5,997
I find it fascinating, "Percy," that you opine confidently about what the Canadian people do or don't like, yet you are apparently not Candian.

I travel to Canada regularly and interact with people in our offices in Canada daily, and I have yet to hear anyone use anything other than meters and grams for distance/weight.

I guess I also find it disheartening that some people seem to actualkly exult in their ignorance: "I'm proud of knowing nothing about the metric system." In almost any other culture I know of, people would not boast of their ignorance, and maybe they'd make the effort to remedy that ignorance.

I mean, really, there's nothing about the metric system that 95+% of the American public could not master if they wished to take the time to learn it. Well I can understand if someone says that they choose not to take the time to learn about the metric system -- they're certainly entitled to use that time doing something else (working, learning about something else, watching soap operas, whatever). But to wave the flag of ignorance and proclaim it gladly to the world -- that seems unfortunate.
Nov 13th, 2009, 05:35 AM
#34

Join Date: Jul 2006
Posts: 437
I love that trick, thanks.
Nov 13th, 2009, 06:06 AM
#35

Join Date: Nov 2009
Posts: 25
As Henry Ford said
"Why waste my time when others can do it for me"
Use a cellphone
Nov 13th, 2009, 08:16 AM
#36

Join Date: Sep 2003
Posts: 181
rizzuto

I happen to know that Percy IS Canadian ,born and raised in Canada.

He is a good e-mail friend of mine and I am also Canadian.

We all grew up with the Imperial systems and when Metric was forced on us , we all learned it , we did not like it but we learned it.

I know the Metric system very well and I NEVER use it and none of my friends use it.

We mentally convert in our minds.

For you to call Percy ( a very well educated man) ignorant , is insulting .

Percy said none of his friends use the metric ( and frankly none of mine do either), but we all can use it and we know the metric system well.

for giving his opinion about the Metric Systems.

I am offended for him and all Canadians.
Nov 13th, 2009, 08:37 AM
#37

Join Date: Jan 2003
Posts: 987
Thanks, Steve, for the Celsius/Centigrade info!

Celia
Nov 13th, 2009, 08:49 AM
#38

Join Date: Mar 2007
Posts: 8,675
What surprised me when visiting a friend in England, driving the highways and seeing the speed limits posted in miles! Duh! Their odometer though was is both miles/km.

Seems there's a mix-n-match, some places.
Nov 13th, 2009, 09:31 AM
#39

Join Date: Apr 2005
Posts: 5,215
Ok, so , what is the "little trick" to go from Fahrenheit to Centigrade? That is converting 80F to 27C?

regards - tom
ps - I don't know one as easy as going the other way
Nov 13th, 2009, 10:57 AM
#40

Join Date: Feb 2003
Posts: 13,216
Gosh , Gee , Thanks jmvp.

How are you doing. Been anywhere recently since coming back from Egypt. ?

Thanks again, but that's okay, rizzuto is entitled to her opinion.

cary999:

I have to apologize ,as I missed your question about why the fraction is 9/5 C

Okay let me take a stab at it and you can correct it,as it has been a while

On the Centigrade System, water freezes at 0 degrees
and it boils at 100 degrees.

On the Farenheit System water freezes at 32 degrees and boils at 212 degrees.

Therefore to change from 0 C to 100 C is equivalent to a change from 32 F to 212 F

Therefore 100 C change in units is = 180 F change in units.

I know,I know , some will say ( not you cary ) that

100C is NOT = to 180 F !!
But yes it is because you are moving from 32F to 212 F , which is 180 units.

Dividing 180/100 = 9/5

You probaly have a better method cary !