in the equation used for the inter -conversion of the two scales of temperature,why fo we subtract 23 from f?

Question

c/5=f-32/9

Answer 1

Because 32 F = 0C, so you subtract 32 when going from degF to degC to get the same 'starting point' (freezing point of water) then do the 5/9 times caluculation to straighten out the difference in how much hotter or colder 1 degree represents on each scale.

Answer 2

For the Celsius and Fahrenheit scales of temperature measurement, two points coincide on the scale, viz the freezing point of water, which is 0 deg C and 32 deg Fahrenheit, and the boiling point of water, which is 100 deg C and 212 deg F. To be able to compare other temperatures on the two scales above and below these points, you need to do as follows:
Imagine the two scales put side by side and applying the law of ratios we get
(F- 32) / (212 - 32) = (C - 0) / ( 100 - 0), or
(F - 32) / 180 = C/ 100
In short, we substract 32 from F because the freezing point on this scale starts from 32 rather than zero as on the C scale.