Question

Explain how you can tell when a formula represents a length an area or a volume

Answer 1

Do you mean how you can tell between an area formula and a volume formula? Well usually like on a reference sheet it says the shape and the letter a or v, a representing area and v representing volume. I hope this helps, if it doesn't please tell me in the comment section

Answer 2

C = 2pi*r, the r represents a length
A = pi*r^2 the r^2 represents a product of length*length which is area
V = (4/3)pi*r^3 the r^3 represents a product of length*length*length which is volume, a sphere

( this is for a circle)