działania na ułamkach dziesietnych i zwyklych rozpisz 4/5* ¼= 4,9*2/7= 1,3: 5,1/5 1,4/5:2,25 1,7:1/20 chodzi o takie coś:

4/5 * 1/4 = 4/20 = 1/5  4,9 * 2/7 = 49/10 * 2/7 = 98/70 = 1 28/70 = 1 2/5  1,3 : 5 1/5 = 13/10 : 26/5 = 13/10 * 5/26 = 65/260 = 1/4  1 4/5 : 2,25 =9/5 :225/100 =9/5 *100/225 = 900/1125 = 4/5 1,7 : 1/20 = 17/10 * 20/1 = 340/10 = 34 

a) 4/5×1/4 = 4×1/5×4=4/20=1/5 b)4,9×2/7= 4i9/10×2/7=49/10×2/7=98/70=1 i 28/70=1 i 2/5 c)1,3 : 5 i 1/5= 1i3/10:26/5=13/10×5/26=65/260=13/56 d)1 i 4/5 :2,25=9/5 : 2 i 25 /100=9/5 : 2 i 1/4 = 9/5 : 9/4 = 9/5 ×4/9 =9 ×4 / 9×5 =36/45= 4/5 e)1,7 : 1/20 = 1 i 7/10 : 1/20= 17/10 × 20/1= 17 × 20/ 10 ×1 = 340/10 = 34