Solution to Pop Question 1


The algorithm works because -40 C = -40 F.  In other words, the
temperature scales are equal at -40.  Therefore by adding 40 to
either temperature, you are simply shifting that axis and re-
setting zero to the point where the two scales are equal.  Then
correcting from one scale to the other is just a matter of
multiplying by the slope of the line, and after making that
calculation you subtract 40 to set the other axis back to the
normal scale.  

Or, stating it as an algebra problem:

       deg F   =   9/5 deg C  +32

Add 40 to both sides of the equation

       deg F  +  40  = 9/5 deg C  +  72
       deg F  +  40  = 9/5 deg C  + 9/5(40)

       deg F  +  40  =  9/5 (deg C + 40)

(Some of you got close to the idea, many of you were way off. 
Those with a reasonable explanation get 2 points, others who tried
but were off the mark will get 1 point.  Only those who replied by
the time I read my mail on Thursday morning will get credit).