If a rectangle has an area of 24cm2 what is the perimeter

You can't tell.  The area doesn't tell you the length and width, and
if you don't know those, then you can't figure out the perimeter.

If the length and width can have fractions or decimals, then there are
an infinite number of possibile perimeters, that ALL have the same area.

If the length and width can only be whole numbers, then there are
4 different possibilities:

1 x 24 cm . . . . . Area = 24 cm² . . . . . Perimeter =  50 cm

2 x 12 cm . . . . . Area = 24 cm² . . . . . Perimeter =  28 cm

3 x 8 cm . . . . . . Area = 24 cm² . . . . . Perimeter =  22 cm

4 x 6 cm . . . . . . Area = 24 cm² . . . . . Perimeter =  20 cm