Dévellope puis effectue les calculs mentalement a. 15 x ( 100 + 2 ) = b. 20 x ( 10 - 1) = c. 4 x ( 25 - 3 ) = d. 25 x ( 8 - 2 ) =

a) 15 X (100 + 2)
= 15 X 100 + 15 X 2
= 1 500 + 30
= 1 530

b) 20 X (10 - 1)
= 20 X 10 + 20 X (- 1)
= 200 - 20
= 180

c) 4 X (25 - 3)
= 4 X 25 + 4 X (- 3)
= 100 - 12
= 88

d) 25 X (8 - 2)
= 25 X 8 + 25 X (- 2)
= 200 - 50
= 150