On converting units of length in meters:
Here is the conversion metric chart:
Kilom - Hectom - Dekam - Meter - Decim - Centim - Millim
Just find the "." on a number, then move it on how many points it reaches the unit desired. If it is a whole number, the dot is always on the right side after the ones digit.
Meter to Kilometer.
670 meters = ? km
Kilom ← ← ← Meter
3 points to the left.
670 ← ← ←
On the english system, you can do like this:
How many foot are there in 90 yards?
(Let us say that you don't know how many foot are there in 1 yard)
If 1 yard = 36 inch
Then 90 yards = 3240 inches.
If 1 inch = 0.0833333 foot
Then 3240 inches = 270 foot
So therefore, there are 270 foot in 90 yards.
I mean, on the English system you just need to remember some equations like on how many inch per foot, yard per inch, inch per yard, etc. and then try to connect them to each other like what I did.