Bonsoir,

utilise le  quadrillage

1) 10 carreaux

10*10 = 100m²

2) 4 + 4 = 8  

8*10 =>  80m²

1)13 careaux +3 carreaux

16 *2 => 32 dm²

2) 6+1 +1

8* 3 => 24 km²