a) a*h/2 = 28cm * 19cm/2 = 532 cm / 2 = 266cm²
3,2 dm = 32 cm
32 cm * 38 cm / 2 = 1216 / 2 = 608cm²
7 dm * 6 dm / 2 = 42 dm / 2 = 21dm²
b) 20cm * 25 cm / 2 = 500cm / 2 = 250cm²
10m * 3m/2 = 30m / 2 = 15m²
32cm * 24cm / 2 = 758cm / 2 = 384cm²
