Amarble slab is 1 metre long and has a rectangular cross section of area 15cm squared. what is the volume of the marble slab?

Supposing that is what you meant we just get the cross section multiplied by the length. 

The problem is they aren't in the same units. Let's convert the length into centimeters first. 
1 m = 100 cm 

So multiply 15 cm² x 100 cm 
= 1,500 cm^3 

 
The volume is 1,500 cm^3

true is the correct answer

hope i

what experimental evidence led scientists to change from the previous model to this one?

a few of the positive particles aimed at a gold foil seemed to bounce back.

the colors of light emitted from heated atoms had very specific energies.

experiments with water vapor showed that elements combine in specific proportions.

cathode rays were bent in the same way whenever a magnet was brought near them.