What do you want to measure about the marble? Its diameter, radius, circumference, volume, mass, density...?
Grams
As it is a marble slab, it could be supposed that the shape is fairly regular. So multiplying length by width will give the square area of the slab. It could be that the square area is not required, and the length and width is needed simply to fit the marble slab into a recess or is to be used as a work-surface , etc. But, either way, a steel tape measure is usually required to measure the marble slab.
If I was you i would use millimetres or centimetres.
You take a graduated cylinder,or anything you can measure water in, and put water in it. You drop the marble in and the change in water height is your volume. For example if the cylinder is filled up to 10ml and after you drop in the marble it goes to 15ml then the marble has a volume of 5ml cubed.
I would use a micrometer. A caliper would do as well.
Grams
cut your ruler as small as u can
As it is a marble slab, it could be supposed that the shape is fairly regular. So multiplying length by width will give the square area of the slab. It could be that the square area is not required, and the length and width is needed simply to fit the marble slab into a recess or is to be used as a work-surface , etc. But, either way, a steel tape measure is usually required to measure the marble slab.
millimetres or mm
milimetersMilliliter
If I was you i would use millimetres or centimetres.
That depends what aspect of a marble you want to measure, for example its diameter, its mass, its density, its color, etc.
You take a graduated cylinder,or anything you can measure water in, and put water in it. You drop the marble in and the change in water height is your volume. For example if the cylinder is filled up to 10ml and after you drop in the marble it goes to 15ml then the marble has a volume of 5ml cubed.
That depends what you want to measure: its diameter, its mass, its weight, its color, etc.
I would use a micrometer. A caliper would do as well.
Mass is measured in kilograms. Weight is measured in newtons. If you are asking which unit to choose to measure then mass of a marble, then you need to use the submultiple of the kilogram, the gram.
If you have calibrated eyeballs