Given:
Side of the square slab = 90 cm
Area of square slab
=90×90=8100 cm2
Area of the floor =81 m2
We know that,
1 m=100 cm1 m2=10,000 cm2
So,
81 m2=81×10,000 =8,10,000 cm2
Number of slabs required
=8100008100=810081=100
Therefore, 100 such square slabs are required to cover the floor.