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

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

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

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.?