Decimal Subtraction

Directions: Use the digits 1 to 9, at most one time each, to make two true statements.

Hint

How do you place digits so the difference is less than ten?

Answer

Number of Unique Solutions: 132
1: 3.9 – 1.4 = 2.5
2: 3.9 – 1.5 = 2.4
3: 3.9 – 2.4 = 1.5
4: 3.9 – 2.5 = 1.4
5: 4.3 – 1.5 = 2.8
6: 4.3 – 1.8 = 2.5
7: 4.3 – 2.8 = 1.5
8: 4.5 – 1.6 = 2.9
9: 4.5 – 1.7 = 2.8
10: 4.5 – 1.8 = 2.7
11: 4.5 – 1.9 = 2.6
12: 4.5 – 2.6 = 1.9
13: 4.5 – 2.9 = 1.6
14: 4.7 – 1.2 = 3.5
15: 4.7 – 1.5 = 3.2
16: 4.7 – 3.2 = 1.5
17: 4.9 – 1.2 = 3.7
18: 4.9 – 1.7 = 3.2
19: 5.7 – 2.1 = 3.6
20: 5.7 – 2.6 = 3.1
21: 5.7 – 3.1 = 2.6
22: 5.7 – 3.6 = 2.1
23: 5.8 – 1.2 = 4.6
24: 5.9 – 1.2 = 4.7
25: 5.9 – 1.7 = 4.2
26: 6.2 – 1.3 = 4.9
27: 6.2 – 1.5 = 4.7
28: 6.2 – 1.7 = 4.5
29: 6.2 – 4.7 = 1.5
30: 6.3 – 1.5 = 4.8
31: 6.3 – 1.8 = 4.5
32: 6.3 – 4.8 = 1.5
33: 6.5 – 1.7 = 4.8
34: 6.5 – 1.8 = 4.7
35: 6.5 – 2.7 = 3.8
36: 6.5 – 2.8 = 3.7
37: 6.5 – 3.7 = 2.8
38: 6.5 – 3.8 = 2.7
39: 6.7 – 1.3 = 5.4
40: 6.7 – 1.8 = 4.9
41: 6.8 – 2.3 = 4.5
42: 6.8 – 2.5 = 4.3
43: 6.8 – 2.7 = 4.1
44: 6.8 – 4.1 = 2.7
45: 6.8 – 4.3 = 2.5
46: 6.8 – 4.5 = 2.3
47: 6.9 – 1.2 = 5.7
48: 6.9 – 1.7 = 5.2
49: 7.1 – 2.3 = 4.8
50: 7.1 – 2.5 = 4.6
51: 7.1 – 2.6 = 4.5
52: 7.1 – 2.8 = 4.3
53: 7.1 – 4.3 = 2.8
54: 7.1 – 4.6 = 2.5
55: 7.1 – 4.8 = 2.3
56: 7.2 – 1.3 = 5.9
57: 7.2 – 1.8 = 5.4
58: 7.3 – 1.4 = 5.9
59: 7.3 – 1.9 = 5.4
60: 7.3 – 2.5 = 4.8
61: 7.3 – 2.8 = 4.5
62: 7.3 – 4.5 = 2.8
63: 7.3 – 4.8 = 2.5
64: 7.5 – 1.2 = 6.3
65: 7.5 – 1.3 = 6.2
66: 7.5 – 2.6 = 4.9
67: 7.5 – 2.9 = 4.6
68: 7.6 – 3.1 = 4.5
69: 7.6 – 3.5 = 4.1
70: 7.6 – 4.1 = 3.5
71: 7.8 – 1.3 = 6.5
72: 7.8 – 1.5 = 6.3
73: 7.8 – 3.2 = 4.6
74: 7.8 – 4.6 = 3.2
75: 7.8 – 6.3 = 1.5
76: 7.9 – 1.4 = 6.5
77: 7.9 – 1.5 = 6.4
78: 7.9 – 6.4 = 1.5
79: 8.1 – 3.5 = 4.6
80: 8.1 – 3.6 = 4.5
81: 8.1 – 4.6 = 3.5
82: 8.3 – 1.4 = 6.9
83: 8.3 – 1.9 = 6.4
84: 8.3 – 2.4 = 5.9
85: 8.3 – 2.9 = 5.4
86: 8.4 – 1.5 = 6.9
87: 8.4 – 1.9 = 6.5
88: 8.4 – 6.9 = 1.5
89: 8.5 – 1.2 = 7.3
90: 8.5 – 1.3 = 7.2
91: 8.5 – 2.1 = 6.4
92: 8.5 – 2.4 = 6.1
93: 8.5 – 3.6 = 4.9
94: 8.5 – 3.9 = 4.6
95: 8.7 – 3.1 = 5.6
96: 8.7 – 3.6 = 5.1
97: 8.9 – 1.4 = 7.5
98: 8.9 – 1.5 = 7.4
99: 8.9 – 2.4 = 6.5
100: 8.9 – 2.5 = 6.4
101: 8.9 – 3.2 = 5.7
102: 8.9 – 3.7 = 5.2
103: 8.9 – 5.2 = 3.7
104: 8.9 – 5.7 = 3.2
105: 8.9 – 6.4 = 2.5
106: 8.9 – 7.4 = 1.5
107: 9.1 – 2.3 = 6.8
108: 9.1 – 2.8 = 6.3
109: 9.1 – 6.3 = 2.8
110: 9.1 – 6.8 = 2.3
111: 9.5 – 1.2 = 8.3
112: 9.5 – 1.3 = 8.2
113: 9.5 – 2.1 = 7.4
114: 9.5 – 2.4 = 7.1
115: 9.5 – 2.7 = 6.8
116: 9.5 – 2.8 = 6.7
117: 9.5 – 3.1 = 6.4
118: 9.5 – 3.4 = 6.1
119: 9.5 – 6.7 = 2.8
120: 9.5 – 6.8 = 2.7
121: 9.6 – 1.2 = 8.4
122: 9.6 – 1.4 = 8.2
123: 9.6 – 2.1 = 7.5
124: 9.6 – 2.5 = 7.1
125: 9.6 – 7.1 = 2.5
126: 9.7 – 1.2 = 8.5
127: 9.7 – 1.5 = 8.2
128: 9.7 – 4.1 = 5.6
129: 9.7 – 4.6 = 5.1
130: 9.7 – 5.1 = 4.6
131: 9.7 – 5.6 = 4.1
132: 9.7 – 8.2 = 1.5

Source: Owen Kaplinsky

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Add Fractions with Decimal Sums

Directions: Using the digits 1 to 9 at most one time each, place a digit …

11 comments

  1. Mrs. Elliott's 5th Graders

    5.9-1.2=4.7
    7.9-8.3=1.6
    3.9-1.5=2.4
    8.7-2.3=6.4
    9.8-6.1=2.7
    8.1-4.6=3.5
    9.5-8.3=1.2
    9.7-8.5=1.2

  2. Rudolf Österreicher

    The “solution”-section is missing a lot of solutions. There are 400 solutions, not just 132:

    3.9 – 1.4 = 2.5
    3.9 – 1.5 = 2.4
    3.9 – 2.4 = 1.5
    3.9 – 2.5 = 1.4
    4.3 – 1.5 = 2.8
    4.3 – 1.6 = 2.7
    4.3 – 1.7 = 2.6
    4.3 – 1.8 = 2.5
    4.3 – 2.5 = 1.8
    4.3 – 2.6 = 1.7
    4.3 – 2.7 = 1.6
    4.3 – 2.8 = 1.5
    4.5 – 1.6 = 2.9
    4.5 – 1.7 = 2.8
    4.5 – 1.8 = 2.7
    4.5 – 1.9 = 2.6
    4.5 – 2.6 = 1.9
    4.5 – 2.7 = 1.8
    4.5 – 2.8 = 1.7
    4.5 – 2.9 = 1.6
    4.6 – 1.7 = 2.9
    4.6 – 1.9 = 2.7
    4.6 – 2.7 = 1.9
    4.6 – 2.9 = 1.7
    4.7 – 1.2 = 3.5
    4.7 – 1.5 = 3.2
    4.7 – 1.8 = 2.9
    4.7 – 1.9 = 2.8
    4.7 – 2.8 = 1.9
    4.7 – 2.9 = 1.8
    4.7 – 3.2 = 1.5
    4.7 – 3.5 = 1.2
    4.8 – 1.2 = 3.6
    4.8 – 1.6 = 3.2
    4.8 – 3.2 = 1.6
    4.8 – 3.6 = 1.2
    4.9 – 1.2 = 3.7
    4.9 – 1.7 = 3.2
    4.9 – 3.2 = 1.7
    4.9 – 3.7 = 1.2
    5.2 – 1.4 = 3.8
    5.2 – 1.8 = 3.4
    5.2 – 3.4 = 1.8
    5.2 – 3.8 = 1.4
    5.4 – 1.6 = 3.8
    5.4 – 1.8 = 3.6
    5.4 – 3.6 = 1.8
    5.4 – 3.8 = 1.6
    5.6 – 1.7 = 3.9
    5.6 – 1.9 = 3.7
    5.6 – 3.7 = 1.9
    5.6 – 3.9 = 1.7
    5.7 – 1.8 = 3.9
    5.7 – 1.9 = 3.8
    5.7 – 2.1 = 3.6
    5.7 – 2.6 = 3.1
    5.7 – 3.1 = 2.6
    5.7 – 3.6 = 2.1
    5.7 – 3.8 = 1.9
    5.7 – 3.9 = 1.8
    5.8 – 1.2 = 4.6
    5.8 – 1.6 = 4.2
    5.8 – 2.1 = 3.7
    5.8 – 2.7 = 3.1
    5.8 – 3.1 = 2.7
    5.8 – 3.7 = 2.1
    5.8 – 4.2 = 1.6
    5.8 – 4.6 = 1.2
    5.9 – 1.2 = 4.7
    5.9 – 1.3 = 4.6
    5.9 – 1.6 = 4.3
    5.9 – 1.7 = 4.2
    5.9 – 2.1 = 3.8
    5.9 – 2.8 = 3.1
    5.9 – 3.1 = 2.8
    5.9 – 3.8 = 2.1
    5.9 – 4.2 = 1.7
    5.9 – 4.3 = 1.6
    5.9 – 4.6 = 1.3
    5.9 – 4.7 = 1.2
    6.1 – 2.4 = 3.7
    6.1 – 2.7 = 3.4
    6.1 – 3.4 = 2.7
    6.1 – 3.7 = 2.4
    6.2 – 1.3 = 4.9
    6.2 – 1.5 = 4.7
    6.2 – 1.7 = 4.5
    6.2 – 1.9 = 4.3
    6.2 – 4.3 = 1.9
    6.2 – 4.5 = 1.7
    6.2 – 4.7 = 1.5
    6.2 – 4.9 = 1.3
    6.3 – 1.5 = 4.8
    6.3 – 1.8 = 4.5
    6.3 – 4.5 = 1.8
    6.3 – 4.8 = 1.5
    6.4 – 2.5 = 3.9
    6.4 – 2.9 = 3.5
    6.4 – 3.5 = 2.9
    6.4 – 3.9 = 2.5
    6.5 – 1.7 = 4.8
    6.5 – 1.8 = 4.7
    6.5 – 2.7 = 3.8
    6.5 – 2.8 = 3.7
    6.5 – 3.7 = 2.8
    6.5 – 3.8 = 2.7
    6.5 – 4.7 = 1.8
    6.5 – 4.8 = 1.7
    6.7 – 1.3 = 5.4
    6.7 – 1.4 = 5.3
    6.7 – 1.8 = 4.9
    6.7 – 1.9 = 4.8
    6.7 – 2.8 = 3.9
    6.7 – 2.9 = 3.8
    6.7 – 3.8 = 2.9
    6.7 – 3.9 = 2.8
    6.7 – 4.8 = 1.9
    6.7 – 4.9 = 1.8
    6.7 – 5.3 = 1.4
    6.7 – 5.4 = 1.3
    6.8 – 2.1 = 4.7
    6.8 – 2.3 = 4.5
    6.8 – 2.5 = 4.3
    6.8 – 2.7 = 4.1
    6.8 – 4.1 = 2.7
    6.8 – 4.3 = 2.5
    6.8 – 4.5 = 2.3
    6.8 – 4.7 = 2.1
    6.9 – 1.2 = 5.7
    6.9 – 1.7 = 5.2
    6.9 – 2.1 = 4.8
    6.9 – 2.8 = 4.1
    6.9 – 4.1 = 2.8
    6.9 – 4.8 = 2.1
    6.9 – 5.2 = 1.7
    6.9 – 5.7 = 1.2
    7.1 – 2.3 = 4.8
    7.1 – 2.5 = 4.6
    7.1 – 2.6 = 4.5
    7.1 – 2.8 = 4.3
    7.1 – 4.3 = 2.8
    7.1 – 4.5 = 2.6
    7.1 – 4.6 = 2.5
    7.1 – 4.8 = 2.3
    7.2 – 1.3 = 5.9
    7.2 – 1.4 = 5.8
    7.2 – 1.8 = 5.4
    7.2 – 1.9 = 5.3
    7.2 – 5.3 = 1.9
    7.2 – 5.4 = 1.8
    7.2 – 5.8 = 1.4
    7.2 – 5.9 = 1.3
    7.3 – 1.4 = 5.9
    7.3 – 1.9 = 5.4
    7.3 – 2.5 = 4.8
    7.3 – 2.8 = 4.5
    7.3 – 4.5 = 2.8
    7.3 – 4.8 = 2.5
    7.3 – 5.4 = 1.9
    7.3 – 5.9 = 1.4
    7.4 – 1.6 = 5.8
    7.4 – 1.8 = 5.6
    7.4 – 2.1 = 5.3
    7.4 – 2.3 = 5.1
    7.4 – 5.1 = 2.3
    7.4 – 5.3 = 2.1
    7.4 – 5.6 = 1.8
    7.4 – 5.8 = 1.6
    7.5 – 1.2 = 6.3
    7.5 – 1.3 = 6.2
    7.5 – 2.6 = 4.9
    7.5 – 2.9 = 4.6
    7.5 – 4.6 = 2.9
    7.5 – 4.9 = 2.6
    7.5 – 6.2 = 1.3
    7.5 – 6.3 = 1.2
    7.6 – 3.1 = 4.5
    7.6 – 3.5 = 4.1
    7.6 – 4.1 = 3.5
    7.6 – 4.5 = 3.1
    7.8 – 1.3 = 6.5
    7.8 – 1.5 = 6.3
    7.8 – 3.2 = 4.6
    7.8 – 3.6 = 4.2
    7.8 – 4.2 = 3.6
    7.8 – 4.6 = 3.2
    7.8 – 6.3 = 1.5
    7.8 – 6.5 = 1.3
    7.9 – 1.4 = 6.5
    7.9 – 1.5 = 6.4
    7.9 – 2.1 = 5.8
    7.9 – 2.3 = 5.6
    7.9 – 2.6 = 5.3
    7.9 – 2.8 = 5.1
    7.9 – 3.1 = 4.8
    7.9 – 3.8 = 4.1
    7.9 – 4.1 = 3.8
    7.9 – 4.8 = 3.1
    7.9 – 5.1 = 2.8
    7.9 – 5.3 = 2.6
    7.9 – 5.6 = 2.3
    7.9 – 5.8 = 2.1
    7.9 – 6.4 = 1.5
    7.9 – 6.5 = 1.4
    8.1 – 2.4 = 5.7
    8.1 – 2.7 = 5.4
    8.1 – 3.2 = 4.9
    8.1 – 3.5 = 4.6
    8.1 – 3.6 = 4.5
    8.1 – 3.9 = 4.2
    8.1 – 4.2 = 3.9
    8.1 – 4.5 = 3.6
    8.1 – 4.6 = 3.5
    8.1 – 4.9 = 3.2
    8.1 – 5.4 = 2.7
    8.1 – 5.7 = 2.4
    8.2 – 1.3 = 6.9
    8.2 – 1.5 = 6.7
    8.2 – 1.7 = 6.5
    8.2 – 1.9 = 6.3
    8.2 – 3.5 = 4.7
    8.2 – 3.7 = 4.5
    8.2 – 4.5 = 3.7
    8.2 – 4.7 = 3.5
    8.2 – 6.3 = 1.9
    8.2 – 6.5 = 1.7
    8.2 – 6.7 = 1.5
    8.2 – 6.9 = 1.3
    8.3 – 1.4 = 6.9
    8.3 – 1.9 = 6.4
    8.3 – 2.4 = 5.9
    8.3 – 2.6 = 5.7
    8.3 – 2.7 = 5.6
    8.3 – 2.9 = 5.4
    8.3 – 5.4 = 2.9
    8.3 – 5.6 = 2.7
    8.3 – 5.7 = 2.6
    8.3 – 5.9 = 2.4
    8.3 – 6.4 = 1.9
    8.3 – 6.9 = 1.4
    8.4 – 1.5 = 6.9
    8.4 – 1.9 = 6.5
    8.4 – 2.1 = 6.3
    8.4 – 2.3 = 6.1
    8.4 – 6.1 = 2.3
    8.4 – 6.3 = 2.1
    8.4 – 6.5 = 1.9
    8.4 – 6.9 = 1.5
    8.5 – 1.2 = 7.3
    8.5 – 1.3 = 7.2
    8.5 – 2.1 = 6.4
    8.5 – 2.4 = 6.1
    8.5 – 3.6 = 4.9
    8.5 – 3.9 = 4.6
    8.5 – 4.6 = 3.9
    8.5 – 4.9 = 3.6
    8.5 – 6.1 = 2.4
    8.5 – 6.4 = 2.1
    8.5 – 7.2 = 1.3
    8.5 – 7.3 = 1.2
    8.6 – 1.2 = 7.4
    8.6 – 1.4 = 7.2
    8.6 – 2.7 = 5.9
    8.6 – 2.9 = 5.7
    8.6 – 3.2 = 5.4
    8.6 – 3.4 = 5.2
    8.6 – 3.7 = 4.9
    8.6 – 3.9 = 4.7
    8.6 – 4.7 = 3.9
    8.6 – 4.9 = 3.7
    8.6 – 5.2 = 3.4
    8.6 – 5.4 = 3.2
    8.6 – 5.7 = 2.9
    8.6 – 5.9 = 2.7
    8.6 – 7.2 = 1.4
    8.6 – 7.4 = 1.2
    8.7 – 2.3 = 6.4
    8.7 – 2.4 = 6.3
    8.7 – 3.1 = 5.6
    8.7 – 3.6 = 5.1
    8.7 – 5.1 = 3.6
    8.7 – 5.6 = 3.1
    8.7 – 6.3 = 2.4
    8.7 – 6.4 = 2.3
    8.9 – 1.3 = 7.6
    8.9 – 1.4 = 7.5
    8.9 – 1.5 = 7.4
    8.9 – 1.6 = 7.3
    8.9 – 2.4 = 6.5
    8.9 – 2.5 = 6.4
    8.9 – 3.2 = 5.7
    8.9 – 3.7 = 5.2
    8.9 – 5.2 = 3.7
    8.9 – 5.7 = 3.2
    8.9 – 6.4 = 2.5
    8.9 – 6.5 = 2.4
    8.9 – 7.3 = 1.6
    8.9 – 7.4 = 1.5
    8.9 – 7.5 = 1.4
    8.9 – 7.6 = 1.3
    9.1 – 2.3 = 6.8
    9.1 – 2.4 = 6.7
    9.1 – 2.7 = 6.4
    9.1 – 2.8 = 6.3
    9.1 – 3.4 = 5.7
    9.1 – 3.7 = 5.4
    9.1 – 5.4 = 3.7
    9.1 – 5.7 = 3.4
    9.1 – 6.3 = 2.8
    9.1 – 6.4 = 2.7
    9.1 – 6.7 = 2.4
    9.1 – 6.8 = 2.3
    9.2 – 1.4 = 7.8
    9.2 – 1.8 = 7.4
    9.2 – 3.4 = 5.8
    9.2 – 3.8 = 5.4
    9.2 – 5.4 = 3.8
    9.2 – 5.8 = 3.4
    9.2 – 7.4 = 1.8
    9.2 – 7.8 = 1.4
    9.3 – 1.5 = 7.8
    9.3 – 1.8 = 7.5
    9.3 – 2.5 = 6.8
    9.3 – 2.8 = 6.5
    9.3 – 4.1 = 5.2
    9.3 – 4.2 = 5.1
    9.3 – 5.1 = 4.2
    9.3 – 5.2 = 4.1
    9.3 – 6.5 = 2.8
    9.3 – 6.8 = 2.5
    9.3 – 7.5 = 1.8
    9.3 – 7.8 = 1.5
    9.4 – 1.6 = 7.8
    9.4 – 1.8 = 7.6
    9.4 – 2.1 = 7.3
    9.4 – 2.3 = 7.1
    9.4 – 3.6 = 5.8
    9.4 – 3.8 = 5.6
    9.4 – 5.6 = 3.8
    9.4 – 5.8 = 3.6
    9.4 – 7.1 = 2.3
    9.4 – 7.3 = 2.1
    9.4 – 7.6 = 1.8
    9.4 – 7.8 = 1.6
    9.5 – 1.2 = 8.3
    9.5 – 1.3 = 8.2
    9.5 – 2.1 = 7.4
    9.5 – 2.4 = 7.1
    9.5 – 2.7 = 6.8
    9.5 – 2.8 = 6.7
    9.5 – 3.1 = 6.4
    9.5 – 3.4 = 6.1
    9.5 – 6.1 = 3.4
    9.5 – 6.4 = 3.1
    9.5 – 6.7 = 2.8
    9.5 – 6.8 = 2.7
    9.5 – 7.1 = 2.4
    9.5 – 7.4 = 2.1
    9.5 – 8.2 = 1.3
    9.5 – 8.3 = 1.2
    9.6 – 1.2 = 8.4
    9.6 – 1.4 = 8.2
    9.6 – 2.1 = 7.5
    9.6 – 2.5 = 7.1
    9.6 – 7.1 = 2.5
    9.6 – 7.5 = 2.1
    9.6 – 8.2 = 1.4
    9.6 – 8.4 = 1.2
    9.7 – 1.2 = 8.5
    9.7 – 1.3 = 8.4
    9.7 – 1.4 = 8.3
    9.7 – 1.5 = 8.2
    9.7 – 3.2 = 6.5
    9.7 – 3.5 = 6.2
    9.7 – 4.1 = 5.6
    9.7 – 4.6 = 5.1
    9.7 – 5.1 = 4.6
    9.7 – 5.6 = 4.1
    9.7 – 6.2 = 3.5
    9.7 – 6.5 = 3.2
    9.7 – 8.2 = 1.5
    9.7 – 8.3 = 1.4
    9.7 – 8.4 = 1.3
    9.7 – 8.5 = 1.2
    9.8 – 2.3 = 7.5
    9.8 – 2.5 = 7.3
    9.8 – 3.1 = 6.7
    9.8 – 3.7 = 6.1
    9.8 – 4.1 = 5.7
    9.8 – 4.2 = 5.6
    9.8 – 4.6 = 5.2
    9.8 – 4.7 = 5.1
    9.8 – 5.1 = 4.7
    9.8 – 5.2 = 4.6
    9.8 – 5.6 = 4.2
    9.8 – 5.7 = 4.1
    9.8 – 6.1 = 3.7
    9.8 – 6.7 = 3.1
    9.8 – 7.3 = 2.5
    9.8 – 7.5 = 2.3

    Granted, you could say “9.8 – 7.5 = 2.3” and “9.8 – 2.3 = 7.5” are equivalent. But this still only cuts down the number of solutions in half. The “solution”-section is missing, for example, all solutions that begin with 9.8.

    Is it because you count 9.8 – 7.5 = 2.3 as the same solution as 8.9 – 5.7 = 3.2 (because the digits in each number are just swapped)?

    I then thought, maybe you counted the different results on both sides of the equation, but there are 59 different results:
    1.2
    1.3
    1.4
    1.5
    1.6
    1.7
    1.8
    1.9
    2.1
    2.3
    2.4
    2.5
    2.6
    2.7
    2.8
    2.9
    3.1
    3.2
    3.4
    3.5
    3.6
    3.7
    3.8
    3.9
    4.1
    4.2
    4.3
    4.5
    4.6
    4.7
    4.8
    4.9
    5.1
    5.2
    5.3
    5.4
    5.6
    5.7
    5.8
    5.9
    6.1
    6.2
    6.3
    6.4
    6.5
    6.7
    6.8
    6.9
    7.1
    7.2
    7.3
    7.4
    7.5
    7.6
    7.8
    8.2
    8.3
    8.4
    8.5

    • Rudolf Österreicher

      Also, the directions say to make “two true statements”, but it’s not possible to make two such statements each using 6 digits and have no digit be repeated. I guess the directions should say “to make *a* true statement”

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