Bài 5:
\(72\cdot61+72\cdot42-216\)
\(=72\left(61+42\right)-72\cdot3\)
\(=72\left(103-3\right)\)
\(=72\cdot100=7200\)
Bài 4:
\(2,2ha=22000m^2\)
\(0,63ha=6300m^2\)
\(5863m^2=0,5863ha\)
\(128m^2=0,0128ha\)
\(3m^28dm^2=3,08m^2\)
\(12m^235cm^2=12,0035m^2\)
\(7km^215ha=7,15km^2\)
\(6m^2128cm^2=6,0128m^2\)