What temperature does Fahrenheit equal Celsius?

That last bit of information about the number 40 doesn't seem to have anything to do with the question at hand (!?!), but is interesting all the same. It's only a semiperfect number EXACTLY because it's the sum of only SOME of its proper divisors (one could either leave out 10, or both 2 and 8). The number 6, on the other hand, is a perfect number, because all its proper divisors **perfectly** add up to 6 (6=1+2+3). The number itself is not included because any number is an improper divisor of itself.

That subset is a little suspect. It doesn’t include 8 . It says we can get to the result we want by ignoring inconvenient elements

Just like the metric system, The U.S.A. will probably never adopt the celcius system. We just have to be different!!