### Brain Teasers

# Conversions

When you convert from an English measurement to a Metric measurement, you multiply by a number. For example, to find out how many kilograms are in 10 pounds, you multiply 10 by .454. To find out how many meters are in 10 yards, you multiply 10 by .914. This is the procedure for every conversion except for one. When you convert from Fahrenheit to Celsius, you subtract 32 and multiply by 1/9.

Why does the temperature conversion require a subtraction and a multiplication, while all the other conversions require just a multiplication?

Why does the temperature conversion require a subtraction and a multiplication, while all the other conversions require just a multiplication?

### Hint

Compare the zeros.### Answer

For distance, weight, and every other measure, a result of zero is the same no matter what the units are. The temperature scales, however, have arbitrary zeros. This means that 0 degrees Celsius and 0 degrees Fahrenheit are not the same temperature.(As an interesting side note, the Kelvin and Rankine scales both have their 0 degrees set to Absolute Zero, so you can convert from one to the other with a simple multiplication.)

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## Comments

Well, actually, you subtract because Celsius sets the freezing point of water as 0Âº and Fahrenheit sets it at 32Âº. likewise, the boiling point of water is 100Âº C, 212Âº F.

The 180 point difference in F as opposed to the 100 point difference in C yeilds the constant - and it's 5/9 from F to C, not 1/9. Conversely, you multiply by 9/5 going form C to F.

The 180 point difference in F as opposed to the 100 point difference in C yeilds the constant - and it's 5/9 from F to C, not 1/9. Conversely, you multiply by 9/5 going form C to F.

Huh, it's quite obvious when you knoew the answer

I didn't get the exact answer, but I do know, if you graph the resulting conversions as linear functions, each line has a unique slope. This means there is a non-linear relationship between the two conversions. Also the two lines intersect at the point (-40,-40) so -40 degrees F= -40 degrees C

If you have a decent understanding of the temperature scales, this isn't much of a teaser, just asking an everyday question. But hey, not everyone does have a good understanding of it, so I'm sure some people learned something here

An interesting corollary is to ask, Why did Dr Fahrenheit set the zero on his scale where he did? Several answers have been suggested, but the most plausible seems to be that he was an experimental chemist and he set his zero to be the coldest termperature that he could conveniently make in his laboratory. Since he was working before modern methods of refrigeration, this was achieved by mixing ice and salt.

I asked my physics teacher a teaser like this before, it was amusing to see him getting frustrated after I told him that the answer was simple, it still took him ten minutes to figure out and then he was embarrassed he didn't get it sooner. Good times.

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