Question

Obilcz.Korzystając z rozdzielczości mnożenia względem dodawania i odejmowania
18 x 40=
13x70=
21x40=
19x30=

Answer 1

18x40=720
13x70=910
21x40=840
19x30=570

Answer 2

18* 40 = (10 +8)*40 = 10*40 + 8*40 = 400 + 320 = 720
18*40 = (20 -2)*40 = 20*40 - 2*40 = 800 - 80 = 720
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13*70 = (10+3)*70 = 10*70 + 3*70 = 700 + 210 = 910
13*70 = (20 -7)*70 = 20*70 - 7*70 = 1400 - 490 = 910
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21 *40 = 20*40 + 1 *40 = 800 + 40 = 840
19*30 = (20 -1)*30 = 20*30 - 1*30 = 600 - 30 = 570

Answer 3

18 x 40= 10x40 + 8x40 = 400 + 320= 720
13 x 70= 10x70 + 3x70 = 700+210 = 910
21 x 40= 20x40 + 1x40= 800 + 40= 840
19 x 30= 10x30 + 9x30= 300 + 270= 570

dostanę naj.?