№13
Будем решать в простых дробях по действиям.
а) 1) 3/9 + 1/6 = 1/3 + 1/6 - 2/6 + 1/6 = 3/6 = 1/2
2) 1/2 *4 = 2
3)23/90 : 1 48/90= 23/90 * 90/138 = 23/138= 1/6
4) 2 : 1/6 = 12
б) 1) 7/9 + 9/99 = 7/9 + 1/11 = 77/99 + 9/99 = 86/99
2) 7,4 - 8,4 = -1
3) 86/99 : (-1) = -86/99
4) 7,3 : 21,9 = 1/3
5)-86/99 + 1/3 = -86/99 + 33/99 = -53/99
в)1)37/90 + 1/9 = 37/90 + 10/90 = 47/90
2) 47/90 * 9/47 = 1/10
3) 32/90 : 5/9 = 32/90 * 9/5= 32/50
4) 32/50 : 32 = 1/50
5) 1/10 : 1/50 = 5
г) 1) 3/3 + 1/3 = 1
2) 1 : 1/4 = 4
3) 111/900 : 925/10000 = 37/300 : 37/400 = 37/300 * 400/37 = 4/3
4) 4 : 37/2775 = 4 * 2775/37 =
5) 12,5 * 0,64 = 1,6
6) 4/3 + 1,6 = 1 1/3 + 1 3/5 = 1 5/15 + 1 9/15 = 2 14/15
№14
7,(9) ≈ 8
0,12(9) = (129 -12)/900= 117/900
-3 ( 89 -8)/90 = -3 81/90 = -3 9/10