Question 561733
what is the formula for Fahrenheit scale is a linear function of temperature on the celsius scale.
Ten degrees celsius equal 50 degrees fahrenheit,and 25 degrees celsius equals 77 degrees fahrenheir

<pre>

1.  Add 40



    Remember the "four F" rule: "Fahrenheit First, Five First"



2.  Multiply by 5  if Fahrenheit is First, otherwise mutiply by 9


3.  Divide by 9 if you multiplied by 5 in step 2, otherwise divide by 5
 
   Notice that steps 2 and 3 are always 5 and 9 or 9 and 5. Five First
    if Fahrenheit is First 



4.  Subtract 40.



--------------------



Suppose we have 50°F to change to Celcius



1.  Add 40°

<font color="red">We get 50°+40°=90°.</font>

    Remember the "four F" rule: "Fahrenheit First, Five First"

<font color="red">We began with °F so we say "Five first".</font>

2.  Multiply by 5  if Fahrenheit is First, otherwise mutiply by 9

<font color="red">We had F first, so we multiply by 5 first and we get 90°x5 = 450°.</font>

3.  Divide by 9 if you multiplied by 5 in step 2, otherwise divide by 5
<font color="red">We multiplied by 5 in step 2, so we divide by 9 and we get 450°÷9 = 50°.</font>
   Notice that steps 2 and 3 are always 5 and 9 or 9 and 5. Five First
    if Fahrenheit is First 

<font color="red">Yes we noticed that</font>

4.  Subtract 40.

<font color="red">We subtract 40° and we get 50°-40° = 10°C.</font>



------------------------------------------------------------



Now let's go backwards and start with 10°C and see if we can get 50°F



1. Add 40°

<font color="red">We get 10°+40°=50°.</font>

Remember the four F rule: "Fahrenheit First, Five First"

<font color="red">We began with °C so we DO NOT say "Five first".</font>

2. Multiply by 5 if Fahrenheit is First, otherwise mutiply by 9

<font color="red">We DO NOT have F first, so we multiply by 9 first and we get 50°x9 = 450°</font>

3. Divide by 9 if you multiplied by 5 in step 2, otherwise divide by 5
<font color="red">We multiplied by 9 in step 2, so we divide by 5 and we get 450°÷5 = 90°.</font>
Notice that steps 2 and 3 are always 5 and 9 or 9 and 5. Five First
if Fahrenheit is First 

<font color="red">Yes we noticed that.</font>

4. Subtract 40.

<font color="red">We subtract 40° and we get 90°-40° = 50°F.</font>



--------------------------------------



Suppose we have 77°F to change to Celcius


1. Add 40°

<font color="red">We get 77°+40°=117°</font>

Remember the "four F" rule: "Fahrenheit First, Five First"

<font color="red">We began with °F so we say "Five first"</font>

2. Multiply by 5 if Fahrenheit is First, otherwise mutiply by 9

<font color="red">We had F first, so we multiply by 5 first and we get 117°x5 = 585°</font>

3. Divide by 9 if you multiplied by 5 in step 2, otherwise divide by 5
<font color="red">We multiplied by 5 in step 2, so we divide by 9 and we get 585°÷9 = 65°</font>
Notice that steps 2 and 3 are always 5 and 9 or 9 and 5. Five First
if Fahrenheit is First 

<font color="red">Yes we noticed that.</font>

4. Subtract 40.

<font color="red">We subtract 40° and we get 65°-40° = 25°C.</font>



------------------------------------------------------------




Now let's go backwards and start with 25°C and see if we can get 77°F


1. Add 40°

<font color="red">We get 25°+40°=65°.</font>

Remember the four F rule: "Fahrenheit First, Five First"

<font color="red">We began with °C so we DO NOT say "Five first".</font>

2. Multiply by 5 if Fahrenheit is First, otherwise mutiply by 9

<font color="red">We DO NOT have F first, so we multiply by 9 first and we get 65°x9 = 585°.</font>

3. Divide by 9 if you multiplied by 5 in step 2, otherwise divide by 5
<font color="red">We multiplied by 9 in step 2, so we divide by 5 and we get 585°÷5 = 117°.</font>
Notice that steps 2 and 3 are always 5 and 9 or 9 and 5. Five First
if Fahrenheit is First 

<font color="red">Yes we noticed that.</font>

4. Subtract 40.

<font color="red">We subtract 40° and we get 117°-40° = 77°F.</font>

--------------------------------------

Edwin</pre>