a) To convert cm^2 to m^2, divide by 10,000 (since there are 10,000 cm^2 in 1 m^2).

100 cm^2 = 100/10,000 m^2 = 0.01 m^2

b) To convert m^2 to cm^2, multiply by 10,000.

4 m^2 5 cm^2 = (4 * 10,000) cm^2 + 5 cm^2 = 40,005 cm^2

c) To convert ha to km^2, divide by 100 (since there are 100 ha in 1 km^2).

20 ha = 20/100 km^2 = 0.2 km^2

d) To convert tạ to kg, multiply by 1000 (since there are 1000 kg in 1 tạ).

7 tạ 50 kg = (7 * 1000) kg + 50 kg = 7050 kg