millimeters
METERS!!!The unit of measurement you would use to measure the width of your classroom is meters.
Inches or centimeters, depending on where you live.
Measure the length and the width. Or if you are feeling particularly energetic, then one of them and the diagonal.
It is any linear unit you want to use, depending on the magnitude of the width and on your particular requirements.
A vernier caliper would be a good way, unless you need a more accurate measurement, in which case I might use a micrometer caliper.
grams
METERS!!!The unit of measurement you would use to measure the width of your classroom is meters.
You would use millimetres.
inches
You could use meters or feet.
You could use feet or metres.
millimetres.
Inches or centimeters, depending on where you live.
Inch, centimeter, or millimeter.
inches
volume= length times width times hight.
For that, use length.