Expert: Josh - 11/4/2004

Question
Hi Josh
You sound like you can help me. I hate work problems, they throw me off really bad.  Can you help me break this problem down.  My teacher wants us to show our work, but I can't figure out how to plug everything in its place.
Water boils at 212 degrees Farenheit.
a) What temp will it boil at Celsius
b) Find the Farenheit temperature of hot tap water at 70 degrees Celsius by solving

               70 = 5/9(F - 32)

Please help. Thank you kindly
Betty  

Answer
Hi Betty,

Let C denote the temperature in degrees celsius, where F is measured in Farenheit.

C and F are related by C=(5/9)*(F-32). ...[#1]

Part a) requires you finding the value of C corresponding to F=212. From [#1], C=(5/9)*(212-32)=5*180/9 =100 Celsius
(as expected).

Part b) is the reverse. It asks you to find the value of F (in Farenheit) corresponding to C=70.
You can rearrange the equation to make F the subject.
There is always just one rule to remember.
Whatever you add/subtract/multiply/divide on one side of the equation (equal sign), you do the same to the other side.

From [#1],
C=(5/9)*(F-32) ...multiply both sides by 9/5
(9/5)*C=F-32   ...add 32 to both sides
F=(9/5)*C+32   ...putting C=70 into this gives you F

Cheers.