Find the number of marble slabs of size 20 cm x 30 cm required to pave the floor of a square room of side 3m.

 

Dear Student
Side of the square room ,a = 3m = 300cm
        Area of square room = a² = 300² = 90000cm²
Size of marble slab = 20 cm x 30 cm 
      Length ,l = 20cm
     Breadth ,b = 30cm
      Area of marble slab = l x b = 20 x 30 = 600cm²


Now 
Number of marbles needed = $\frac{Area of square room }{Area of one marble slab} = \frac{90000}{600} = 150$

Number of marbles needed = 150

Regards