To: Editor of cribsheet at Washington Post:
What an absolutely horrible idea for learning metric prefixes!
You suggested:
> King--kilo-
> Henry's--hecto-
> Dirty--deka-
> Underwear--unit (meter, liter, gram)
> Does--deci-
> Contain--centi-
> Mildew--milli-
This memory device is based on the erroneous idea that one must learn the
more or less rarely used prefixes of hecto, deka and deci, while ignoring
the more important (and used) prefixes like mega, giga, micro and perhaps
nano.
Here is a much more useful series of prefixes to learn, with their symbols
(aranged from large to small):
giga (G)
mega (M)
kilo (k)
(unit)
milli (m)
micro (�)*
nano (n)
*( The symbol for micro is the lower case Greek letter, mu. I have typed it
in this email as "�" , which looks correct on my computer. However, it
does not always come through email transmssion correctly so it may give you
an erroneous symbol. Sorry.)
Most of the prefixes in the SI metric system go up or down in steps of 1000,
not steps of 10. Thus (using lengths as an example), we have the simple
pattern:
1 Gm = 1000 Mm
1 Mm = 1000 km
1 km = 1000 m
1 m = 1000 mm
1 mm = 1000 �m
1 �m = 1000 nm
There are more prefixes than those above, five larger than giga and five
smaller than nano, all differing by a factor of 1000. These super-large and
super-small prefixes need not be learned unless one encounters special
situations in which they are useful.
Admittedly, the prefix centi, which is in common use for centimetres, does
not fit this pattern of steps of 1000 . However, it can be taught as a
special exception. The prefixes deci, deka and hecto also do not fit this
pattern but they are seldom used anyway, so they can be largely ignored.
Now if some bright student would come up with a cute phrase for remembering
the sequence giga, mega, kilo, (unit), milli, micro and nano, we might have
something useful.
Sincerely,
Bill Hooper
