a)
12 x 19 = 228 cm2
57 x 11,2 = 5,7 x 11,2 = 63,84 cm2
7,5 x 12,4 = 93 m2
b)
4 x 9/ 2= 36/2= 18 cm2
7x2 4x2 14 x 8/2= 112/2= 56 m2
35cm x 5dm2= 35x 50/2= 1750/2= 875
c)
10 x 10/2= 100/2= 50cm2
4,5 dm x 2 9dm x 9dm/2= 81/2= 40,5
3,2 x 3,2/ 2= 10,24/2= 5,12
