Bonjour pouvez m’aider merci Exercice 1 : Calculer (sans calculatrice) :
a) 12×7 c) 3×17 e) 33×99 g) 42×2,1
b) 87×101 d) 19×8
f) 43×999 h) 28×105
a) 12×7 c) 3×17 e) 33×99 g) 42×2,1
b) 87×101 d) 19×8
f) 43×999 h) 28×105
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Verified answer
Explications étape par étape:
a = 7(10 + 2 ) = 70 + 14 = 84
b = 87 (100 + 1) = 8 700 + 87 = 8 787
c = 3(20 - 3) = 60 - 9 = 51
d = 8(20 - 1) = 160 - 8 = 152
e = 33(100 - 1) = 3 300 - 33 = 3 267
f = 43(1 000 - 1) = 43 000 - 43 = 42 957
Réponse :
bonjour
Explications étape par étape :
a) 12×7
=7x(10+2)
=x10+7x2
=70+14
=84
c) 3×17
=3x(20-3)
3x20-3x3
=60-9
=51
e) 33×99
=33x(100-1)
=33x100-1x33
=3300-33
=3 267
g) 42×2,1
=2.1x40 +2.1x2
=84+4.2
=88.2
b) 87×101
=87x(100+1)
=87x100 +87x1
=8700+87
=8787
d) 19×8
=8x(20-1)
=8x20 -8x1
=160-8
=152
f) 43×999
=43x(1000-1)
=43x1000- 43x1
=43 000 -43
=42 957
h) 28×105
=105x(30-2)
=105x30 -2x105
=3150-210
=2940