How many paving slabs needed 600x600mm to fill 9 square meters?

Area of slab = 0.6 m * 0.6 m = 0.36 sq metres

Minimum number of slabs required = 9/0.36 = 25.

This minimum number is based on the assumption that the area to be covered is a reasonable shape so that only a few slabs need cutting and that all the resultant offcuts are used - even if part of the area looks like crazy paving!