Question

用5 7 8 9 四个数凑成24 有几种方法？

Answer 1

1: (5 + 7 - 9) × 8
2: ((5 + 7) - 9) × 8
3: (5 + (7 - 9)) × 8
4: 5 × 8 -(7 + 9)
5: (5 × 8) - (7 + 9)
6: 5 × 8 - 7 - 9
7: (5 × 8) - 7 - 9
8: (5 × 8 - 7) - 9
9: ((5 × 8) - 7) - 9
10: 5 × 8 -(9 + 7)
11: (5 × 8) - (9 + 7)
12: 5 × 8 - 9 - 7
13: (5 × 8) - 9 - 7
14: (5 × 8 - 9) - 7
15: ((5 × 8) - 9) - 7
16: (5 - 9 + 7) × 8
17: ((5 - 9) + 7) × 8
18: (5 - (9 - 7)) × 8
19: (7 + 5 - 9) × 8
20: ((7 + 5) - 9) × 8
21: (7 + (5 - 9)) × 8
22: (7 - 9 + 5) × 8
23: ((7 - 9) + 5) × 8
24: (7 - (9 - 5)) × 8
25: 8 × (5 + 7 - 9)
26: 8 × ((5 + 7) - 9)
27: 8 × (5 + (7 - 9))
28: 8 × 5 -(7 + 9)
29: (8 × 5) - (7 + 9)
30: 8 × 5 - 7 - 9
31: (8 × 5) - 7 - 9
32: (8 × 5 - 7) - 9
33: ((8 × 5) - 7) - 9
34: 8 × (5 - 9 + 7)
35: 8 × ((5 - 9) + 7)
36: 8 × 5 -(9 + 7)
37: (8 × 5) - (9 + 7)
38: 8 × 5 - 9 - 7
39: (8 × 5) - 9 - 7
40: (8 × 5 - 9) - 7
41: ((8 × 5) - 9) - 7
42: 8 × (5 - (9 - 7))
43: 8 × (7 + 5 - 9)
44: 8 × ((7 + 5) - 9)
45: 8 × (7 + (5 - 9))
46: 8 × (7 - 9 + 5)
47: 8 × ((7 - 9) + 5)
48: 8 × (7 - (9 - 5))

Answer 2

4种