Best Answer:
This is some extremely easy stuff, if you try.

What you need to do is look at a chart and understand the relationship between the prefixes and units.

Units are what you are measuring...length in meters or feet or miles, time seconds or days or centuries, or maybe weight in grams or pounds.

If you are using meters to measure length or distance, Meters may be inconvenient to use, such as how large is an atom, or haw far is the moon.

So what we do is create prefixes. Let's say you want to measure your height. Meters (like yards) is a little inconvenient, because if you are 6 feet tall, you would be 1.83m, but still doable.

Let's say we want to measure how far light travels in one second, 300000000 meters. We write it as 300,000,000 meters. you can see how much easier it is now to read, but still a little cumbersome. So we come up with a prefix that means 1 million. We call it Mega. You have probably heard of Megabucks or Megabytes, or Megahertz. We add Mega to the front of a word to mean million. Back to the distance light travels in one second, 300 Megameters means 300 million meters and we abbreviate it as 300Mm (not to be confused with 300mm). It just means we multiply the number times 1,000,000.

Prefixes go larger, like times 1,000,000 and it smaller like divide by 1,000,000. We call this micro. So a micrometer is one millionth of a meter.

Notice how we use commas to separate the zeros (1,000,000,000 or .000,000,001) It is common to do the same with prefixes. one thousand (kilo), one million (Mega), one billion (Giga)...or smaller, one thousandth (milli), one millionth (micro), one billionth (nano). The upper or lower case is important, M equals Mega and m equals milli. You just have to memorize it.

When we get less than a thousand (or thousandth) we use deca (10 times) hecto (100 times) or deci (divide by 10) or centi (divide by 100)

Your question, milli is a meter divided by 1000, and you have 200 parts of a thousand 200/1000 which is .2 meters.. or if you divide the meter by 100 (centi) you have 20 centimeters 20/100. if you divide the meter by 1 million, um, you have 200,000 um, 200,000/1,000,000).

The last Mn is Megameters. .000,000,2 Mm.

The units in your questions are out of order and can be confusing. Put them in order. relate them to the chart. Don't just take my answer, understand the concept. You will use it the rest of your life.

.000.000.2 Mm

.000.2km

.002hm

.02dam

.2m

2dm

20cm

200mm

200,000um

Source(s):
http://www.simetric.co.uk/siprefix.htm

http://micro.magnet.fsu.edu/primer/java/scienceopticsu/powersof10/

http://www.nikon.com/about/feelnikon/universcale/index.htm

Anonymous
· 1 decade ago