Expert: Bobby Soltani - 7/4/2005

Question
at what temperature have the centigrade and fahrenheit readings the samenumerical value?
please explain how.


Answer
Hi Ahmed,

The formula for converting centigrade from fahrenheit is

Tf = (9/5)*Tc+32

If Tf = Tc, then we can substitute Tc for Tf in the equation above and solve for Tc.

Tc = (9/5)*Tc + 32
subtract Tc from both sides
0 = (4/5)*Tc + 32
subtract 32 from both sides
-32 = (4/5)*Tc
multiply both sides by 5/4
-40 = Tc
and since Tf = Tc,
Tf = -40 also.

So the answer is at -40 degrees, the readings will have the same numerical value on both scales.  Let me know if you have any questions.

Bobby