Metric System: decimal places and -re

When you tutor sciences, you’re immersed in the metric system.  Let’s talk a bit about it.

The metric system uses multiples of 10.  Therefore, to convert from any metric unit to any other one, you just need to move the decimal point;  you needn’t do any math.   However, you do need to know the metric prefixes, so you know how many places to move the decimal:

metre (m)
gram (g)
litre (L)
0.001 0.01 0.1 1 10 100 1000

From the table above, you can see that 1 metre = 0.001 kilometres.  Or, using abbreviations, 1 m = 0.001 km.

Note that the prefixes have their own abbreviations, and the base units (metre, gram and litre) have their own.  mm can’t be confusing because the m in front is the abbreviation for the prefix milli, whereas m in the back is for metre.  Similarly, dL would mean decilitre.

People often ask about the capital L for litre.  It’s true that except for L (and a few other rare instances we won’t get into), you should never use uppercase letters for the metric system.  The reason for the exception with L is that a lowercase l can look like a 1.  To avoid the possible misunderstanding, “l” for litre is either written capital or else in handwriting.

Now, to convert from one unit to the other:  the table tells all.  They key is knowing where the decimal is now, and how many places you’ll have to move it.  For instance, imagine you have 32 cm and you want hm (hectometres). Looking at the chart, you see that from centi to hecto is four jumps left.  (Don’t count centi; count the jumps to hecto).  Therefore, we must move the decimal four jumps left as well.  (In 32, the decimal is of course at the end, since it’s not written.)

32 cm=0.0032 hm

Another example:  how many cm is 2.3m?  Well, looking at the chart, we see centi is two jumps right from metre.  So, move the decimal two jumps right:

2.3m = 230cm

You knew that anyway, since of course there are 100 cm in a metre :)

One more thing:  in metric, it’s -re, not -er.

Jack of Oracle Tutoring by Jack and Diane, Campbell River, BC


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