Hello Poonam
Short answer
Rs 20 / m2 = Rs 20 / (100 cm)2 = Rs 20/104 cm2 = Rs 2/103 cm2 = Rs 0.002 cm2
Long answer
Cost of 1 m2 = Rs 20
Cost of (1 m)2 = Rs 20
Cost of (100 cm)2 = Rs 20
Cost of 10000 cm2 = Rs 20
Cost of 1 cm2 = Rs 20/10000
Cost of 1 cm2 = Rs 0.002