Calcule en pensant au nombre de groupes de 10.

2 x 60 =	30 x 5 =	4 x 40 =	50 x 2 =
20 x 4 =	6 x 30 =	70 x 2 =	60 x 4 =
5 x 40 =	50 x 5 =	9 x 20 =	40 x 3 =