Question

a carpenter is making a circular table top with circumference 4.5 what is the radius of the table top in centmetres

Answer 1

If 4.5 is also in centimeters, than you divide 4.5 by pie and 2. This gives you about 0.717 cm.

Answer 2

That's going to depend completely on the unit of
the 4.5 which, sadly, you have not mentioned.