math
posted by Rashad .
45g=? mg
3.7m= ? cm
2.34 kL= ? L
720cm= ? m
64kg= ? g

Use Google as a converter.
These queries:
45 grams in milligrams (or '45g in mg')
3.7m in cm
2.34kilolitres in litres
etc.
Will all convert for you. 
45 g = ? mg
Since there are 1000 grams in 1 mg, multiply 45 by 1,000 to find this answer.
45 g = 45,000 mg
1 meter = 100 cm. Multiply 3.7 by 100.
If you post the answers to the rest of your problems, we'll be glad to check them. This site will help you.
http://mathforum.org/library/drmath/sets/select/dm_metric.html 
You need to learn how to do these yourself. Here is a table that may help.
kilo
hecta
deca
unit(gram, liter, meter, second, etc)
deci
centi
milli
Going up the table, move the decimal point to the left. Going down the table, move the decimal point to the right. For example, 45 g = ? mg. Place your pencil point on unit (for gram). Going down we move the decimal point to the right. We move 1 place to get to deci, another to get to centi and another to get to milli. That's three places. So 45. g becomes 45,000 mg. Another, 720 cm = ? m. Place the pencil point on cm and we must move up to obtain m; therefore, we move the decimal point to the left. We move 1 place from cm to deci, another to units(meter). That't two places. So 720 cm = 7.20 m. That's all there is to it. Post your answers if you want us to check them. 
You can do these problems in slightly different ways. I prefer to do it using the "passive method", e.g.:
3.7m = 3.7* 100 cm = 370 cm
Here I just substituted m = 100 cm.