Activité 11 - Calcul mental

d)

Calcule en trouvant un procédé simple.


24 . 3 + 12 . 4
= 12 . 2 . 3 + 12 . 4
= 12 . 6 + 12 . 4
= 12 . (6 + 4)
= 12 . 10
= 120
63 . 30 + 21 . 10
= 63 . 30 + 7 . 3 . 10
= 63 . 30 + 7 . 30
= 30 . (63 + 7)
= 30 . 70
= 2100
75 . 12 + 50 . 32
= 25 . 3 . 12 + 25 . 2 . 32
= 25 . 36 + 25 . 64
= 25 . (36 + 64)
= 25 . 100
= 2500