Re: Driving rules of the road in Canada vs. USMike O'Sullivan wrote:
> James Silverton wrote:
>> Rudy wrote on Mon, 16 Jun 2008 18:55:46 GMT:
>>
>>>> My own method for the temperature conversion is to know it
>>>> in units of ten and fill in between using 2 instead of the
>>>> correct 1.8. For example, 50F is 10C, 68F is 20C, 86F is
>>>> 30C., so 14C would be about 58F (a small error but who
>>>> cares.)
>>>>
>>>> An accurate and easy to remember rule is add on 40, multiply by
>>>> the
>>>> factor, subtract 40.
>>
>>> "EASY to remember" , you're joking, right ????
>>
>> It's a damn siight easier than "Do I add on or subtract 32 and at
>> what point?" especially since it works for conversions in both
>> directions!
>>
> Easy!
>
> Celsius to Fahrenheit - double it, deduct 10%, then add 32.
Thats 10 percent of what you get after doubling. Gives an exact
conversion.
> Kilometres to miles - Halve it, then add a quarter. Very accurate!
Just to be clear, you add a quarter of what you get after you halve
it. So, 100km, halve it gives 50, add a quarter of 50 = 12.5 and
you've got 62.5, close enough to the actual 62.1 that you're not going
to get in trouble.
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--John
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(was jclarke at eye bee em dot net)