Question: In this sum, each of the letters represents a different non-zero digit:
$AMC + AMC + AMC + AMC + AMC + AMC + AMC + AMC = FUN$.
Which digit does the letter $N$ represent?
1. **State the problem:** We have the addition:
$$AMC + AMC + AMC + AMC + AMC + AMC + AMC + AMC = FUN$$
where each letter represents a different non-zero digit.
2. **Rewrite the sum:** Since $AMC$ is added 8 times, this is:
$$8 \times AMC = FUN$$
3. **Express $AMC$ and $FUN$ as numbers:**
Let $A$, $M$, $C$, $F$, $U$, and $N$ be digits.
Then:
$$AMC = 100A + 10M + C$$
$$FUN = 100F + 10U + N$$
4. **Set up the equation:**
$$8 \times (100A + 10M + C) = 100F + 10U + N$$
5. **Analyze constraints:**
- $A$, $M$, $C$, $F$, $U$, $N$ are distinct non-zero digits.
- $8 \times AMC$ is a three-digit number $FUN$.
6. **Try to find $A$:**
Since $8 \times AMC$ is three digits, $AMC$ must be between 100 and 124 (because $8 \times 125 = 1000$ which is four digits).
7. **Try $A=1$:**
Then $AMC = 100 + 10M + C$.
Multiply by 8:
$$8 \times (100 + 10M + C) = 800 + 80M + 8C = 100F + 10U + N$$
8. **Check possible values:**
Since $F$ is the hundreds digit of the product, $F=8$.
9. **Rewrite:**
$$800 + 80M + 8C = 800 + 10U + N$$
So:
$$80M + 8C = 10U + N$$
10. **Simplify by dividing by 2:**
$$40M + 4C = 5U + \frac{N}{2}$$
Since $N$ must be an integer digit, $N$ must be even.
11. **Try values for $M$ and $C$ to satisfy:**
We want $10U + N = 80M + 8C$.
12. **Try $M=3$, $C=4$:**
$$80 \times 3 + 8 \times 4 = 240 + 32 = 272$$
So $10U + N = 272$ which is impossible since $10U + N$ is two digits.
13. **Try $M=2$, $C=3$:**
$$80 \times 2 + 8 \times 3 = 160 + 24 = 184$$
So $10U + N = 184$ impossible.
14. **Try $M=1$, $C=6$:**
$$80 \times 1 + 8 \times 6 = 80 + 48 = 128$$
$10U + N = 128$ impossible.
15. **Try $M=0$, $C=5$:**
$M$ cannot be zero (non-zero digits).
16. **Try $M=4$, $C=6$:**
$$80 \times 4 + 8 \times 6 = 320 + 48 = 368$$
$10U + N = 368$ impossible.
17. **Try $M=1$, $C=7$:**
$$80 + 56 = 136$$
$10U + N = 136$ impossible.
18. **Try $M=2$, $C=1$:**
$$160 + 8 = 168$$
$10U + N = 168$ impossible.
19. **Try $M=3$, $C=2$:**
$$240 + 16 = 256$$
$10U + N = 256$ impossible.
20. **Try $M=4$, $C=1$:**
$$320 + 8 = 328$$
$10U + N = 328$ impossible.
21. **Try $M=5$, $C=2$:**
$$400 + 16 = 416$$
$10U + N = 416$ impossible.
22. **Try $M=6$, $C=3$:**
$$480 + 24 = 504$$
$10U + N = 504$ impossible.
23. **Try $M=7$, $C=4$:**
$$560 + 32 = 592$$
$10U + N = 592$ impossible.
24. **Try $M=8$, $C=5$:**
$$640 + 40 = 680$$
$10U + N = 680$ impossible.
25. **Try $M=9$, $C=6$:**
$$720 + 48 = 768$$
$10U + N = 768$ impossible.
26. **Try $A=1$, $M=2$, $C=4$:**
$$AMC = 124$$
$$8 \times 124 = 992$$
So $FUN = 992$
27. **Check digits:**
$F=9$, $U=9$, $N=2$
Digits are $A=1$, $M=2$, $C=4$, $F=9$, $U=9$, $N=2$
$U$ and $F$ are both 9, which violates distinct digits.
28. **Try $A=1$, $M=3$, $C=5$:**
$$AMC = 135$$
$$8 \times 135 = 1080$$ four digits, invalid.
29. **Try $A=1$, $M=1$, $C=8$:**
$$AMC = 118$$
$$8 \times 118 = 944$$
$F=9$, $U=4$, $N=4$ repeated digits, invalid.
30. **Try $A=1$, $M=4$, $C=7$:**
$$AMC = 147$$
$$8 \times 147 = 1176$$ four digits, invalid.
31. **Try $A=1$, $M=5$, $C=3$:**
$$AMC = 153$$
$$8 \times 153 = 1224$$ four digits, invalid.
32. **Try $A=1$, $M=6$, $C=2$:**
$$AMC = 162$$
$$8 \times 162 = 1296$$ four digits, invalid.
33. **Try $A=1$, $M=7$, $C=3$:**
$$AMC = 173$$
$$8 \times 173 = 1384$$ four digits, invalid.
34. **Try $A=1$, $M=8$, $C=4$:**
$$AMC = 184$$
$$8 \times 184 = 1472$$ four digits, invalid.
35. **Try $A=1$, $M=9$, $C=5$:**
$$AMC = 195$$
$$8 \times 195 = 1560$$ four digits, invalid.
36. **Try $A=2$:**
$AMC$ between 200 and 249 (since $8 \times 250 = 2000$ four digits).
37. **Try $A=2$, $M=1$, $C=7$:**
$$AMC = 217$$
$$8 \times 217 = 1736$$ four digits, invalid.
38. **Try $A=2$, $M=3$, $C=4$:**
$$AMC = 234$$
$$8 \times 234 = 1872$$ four digits, invalid.
39. **Try $A=2$, $M=4$, $C=5$:**
$$AMC = 245$$
$$8 \times 245 = 1960$$ four digits, invalid.
40. **Try $A=3$:**
$AMC$ between 300 and 312 (since $8 \times 313 = 2504$ four digits).
41. **Try $A=3$, $M=1$, $C=2$:**
$$AMC = 312$$
$$8 \times 312 = 2496$$ four digits, invalid.
42. **Try $A=3$, $M=0$, $C=1$:**
$M=0$ invalid (non-zero digits).
43. **Try $A=4$ or higher:**
$8 \times 400 = 3200$ four digits, invalid.
44. **Conclusion:**
The only valid $AMC$ is $124$ with $FUN=992$ but digits $F$ and $U$ are the same.
45. **Reconsider the problem:**
Since $F$ and $U$ must be distinct, try to find another approach.
46. **Try to find $N$ from the units digit:**
Units digit of $8 \times C = N$ (mod 10).
47. **Try possible $C$ and $N$ pairs:**
For $C=1$, $8 \times 1=8$, so $N=8$.
For $C=2$, $8 \times 2=16$, $N=6$.
For $C=3$, $8 \times 3=24$, $N=4$.
For $C=4$, $8 \times 4=32$, $N=2$.
For $C=5$, $8 \times 5=40$, $N=0$ invalid (zero digit).
For $C=6$, $8 \times 6=48$, $N=8$.
For $C=7$, $8 \times 7=56$, $N=6$.
For $C=8$, $8 \times 8=64$, $N=4$.
For $C=9$, $8 \times 9=72$, $N=2$.
48. **Try $N=2$ with $C=4$ or $9$:**
Try $C=4$, $N=2$.
49. **Try $A=1$, $M=3$, $C=4$:**
$$AMC = 134$$
$$8 \times 134 = 1072$$ four digits, invalid.
50. **Try $A=1$, $M=2$, $C=4$:**
$$AMC = 124$$
$$8 \times 124 = 992$$ three digits, $N=2$ matches.
51. **Check digits:**
$A=1$, $M=2$, $C=4$, $F=9$, $U=9$, $N=2$
$F$ and $U$ are the same digit, invalid.
52. **Try $N=4$ with $C=3$ or $8$:**
Try $C=3$, $N=4$.
53. **Try $A=1$, $M=5$, $C=3$:**
$$AMC = 153$$
$$8 \times 153 = 1224$$ four digits, invalid.
54. **Try $A=1$, $M=6$, $C=3$:**
$$AMC = 163$$
$$8 \times 163 = 1304$$ four digits, invalid.
55. **Try $N=6$ with $C=2$ or $7$:**
Try $C=2$, $N=6$.
56. **Try $A=1$, $M=1$, $C=2$:**
$$AMC = 112$$
$$8 \times 112 = 896$$
$F=8$, $U=9$, $N=6$
57. **Check digits distinctness:**
$A=1$, $M=1$ repeated digits invalid.
58. **Try $A=1$, $M=3$, $C=2$:**
$$AMC = 132$$
$$8 \times 132 = 1056$$ four digits, invalid.
59. **Try $A=1$, $M=4$, $C=2$:**
$$AMC = 142$$
$$8 \times 142 = 1136$$ four digits, invalid.
60. **Try $A=1$, $M=5$, $C=2$:**
$$AMC = 152$$
$$8 \times 152 = 1216$$ four digits, invalid.
61. **Try $N=8$ with $C=1$ or $6$:**
Try $C=1$, $N=8$.
62. **Try $A=1$, $M=2$, $C=1$:**
$$AMC = 121$$
$$8 \times 121 = 968$$
$F=9$, $U=6$, $N=8$
63. **Check digits distinctness:**
$A=1$, $M=2$, $C=1$ repeated digits invalid.
64. **Try $A=1$, $M=3$, $C=1$:**
$$AMC = 131$$
$$8 \times 131 = 1048$$ four digits, invalid.
65. **Try $A=1$, $M=4$, $C=1$:**
$$AMC = 141$$
$$8 \times 141 = 1128$$ four digits, invalid.
66. **Try $A=1$, $M=5$, $C=1$:**
$$AMC = 151$$
$$8 \times 151 = 1208$$ four digits, invalid.
67. **Try $A=1$, $M=6$, $C=1$:**
$$AMC = 161$$
$$8 \times 161 = 1288$$ four digits, invalid.
68. **Try $A=1$, $M=7$, $C=1$:**
$$AMC = 171$$
$$8 \times 171 = 1368$$ four digits, invalid.
69. **Try $A=1$, $M=8$, $C=1$:**
$$AMC = 181$$
$$8 \times 181 = 1448$$ four digits, invalid.
70. **Try $A=1$, $M=9$, $C=1$:**
$$AMC = 191$$
$$8 \times 191 = 1528$$ four digits, invalid.
71. **Try $N=4$ with $C=8$:**
$$8 \times 8 = 64$$ units digit $4$ matches $N=4$.
72. **Try $A=1$, $M=2$, $C=8$:**
$$AMC = 128$$
$$8 \times 128 = 1024$$ four digits, invalid.
73. **Try $A=1$, $M=3$, $C=8$:**
$$AMC = 138$$
$$8 \times 138 = 1104$$ four digits, invalid.
74. **Try $A=1$, $M=4$, $C=8$:**
$$AMC = 148$$
$$8 \times 148 = 1184$$ four digits, invalid.
75. **Try $A=1$, $M=5$, $C=8$:**
$$AMC = 158$$
$$8 \times 158 = 1264$$ four digits, invalid.
76. **Try $A=1$, $M=6$, $C=8$:**
$$AMC = 168$$
$$8 \times 168 = 1344$$ four digits, invalid.
77. **Try $A=1$, $M=7$, $C=8$:**
$$AMC = 178$$
$$8 \times 178 = 1424$$ four digits, invalid.
78. **Try $A=1$, $M=8$, $C=8$:**
$M$ and $C$ same digit invalid.
79. **Try $A=1$, $M=9$, $C=8$:**
$$AMC = 198$$
$$8 \times 198 = 1584$$ four digits, invalid.
80. **Try $N=2$ with $C=4$ or $9$ again:**
$C=4$, $N=2$ tried before.
81. **Try $A=1$, $M=2$, $C=4$:**
$$AMC = 124$$
$$8 \times 124 = 992$$
$F=9$, $U=9$, $N=2$ repeated digits invalid.
82. **Try $C=9$, $N=2$:**
$$8 \times 9 = 72$$ units digit 2 matches $N=2$.
83. **Try $A=1$, $M=2$, $C=9$:**
$$AMC = 129$$
$$8 \times 129 = 1032$$ four digits, invalid.
84. **Try $A=1$, $M=3$, $C=9$:**
$$AMC = 139$$
$$8 \times 139 = 1112$$ four digits, invalid.
85. **Try $A=1$, $M=4$, $C=9$:**
$$AMC = 149$$
$$8 \times 149 = 1192$$ four digits, invalid.
86. **Try $A=1$, $M=5$, $C=9$:**
$$AMC = 159$$
$$8 \times 159 = 1272$$ four digits, invalid.
87. **Try $A=1$, $M=6$, $C=9$:**
$$AMC = 169$$
$$8 \times 169 = 1352$$ four digits, invalid.
88. **Try $A=1$, $M=7$, $C=9$:**
$$AMC = 179$$
$$8 \times 179 = 1432$$ four digits, invalid.
89. **Try $A=1$, $M=8$, $C=9$:**
$$AMC = 189$$
$$8 \times 189 = 1512$$ four digits, invalid.
90. **Try $A=1$, $M=9$, $C=9$:**
$M$ and $C$ same digit invalid.
91. **Try $N=8$ with $C=1$ or $6$ again:**
$C=6$, $N=8$.
92. **Try $A=1$, $M=2$, $C=6$:**
$$AMC = 126$$
$$8 \times 126 = 1008$$ four digits, invalid.
93. **Try $A=1$, $M=3$, $C=6$:**
$$AMC = 136$$
$$8 \times 136 = 1088$$ four digits, invalid.
94. **Try $A=1$, $M=4$, $C=6$:**
$$AMC = 146$$
$$8 \times 146 = 1168$$ four digits, invalid.
95. **Try $A=1$, $M=5$, $C=6$:**
$$AMC = 156$$
$$8 \times 156 = 1248$$ four digits, invalid.
96. **Try $A=1$, $M=6$, $C=6$:**
$M$ and $C$ same digit invalid.
97. **Try $A=1$, $M=7$, $C=6$:**
$$AMC = 176$$
$$8 \times 176 = 1408$$ four digits, invalid.
98. **Try $A=1$, $M=8$, $C=6$:**
$$AMC = 186$$
$$8 \times 186 = 1488$$ four digits, invalid.
99. **Try $A=1$, $M=9$, $C=6$:**
$$AMC = 196$$
$$8 \times 196 = 1568$$ four digits, invalid.
100. **Try $N=4$ with $C=3$ or $8$ again:**
$C=3$, $N=4$ tried before.
101. **Try $A=1$, $M=2$, $C=3$:**
$$AMC = 123$$
$$8 \times 123 = 984$$
$F=9$, $U=8$, $N=4$
102. **Check digits distinctness:**
$A=1$, $M=2$, $C=3$, $F=9$, $U=8$, $N=4$ all distinct and non-zero.
103. **Answer:**
The digit $N$ represents is $4$.
**Final answer:** $\boxed{4}$