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 is a different non-zero digit. We want to find the digit represented by $N$.
2. **Rewrite the sum:** Since $AMC$ is added 8 times, this is equivalent to:
$$8 \times AMC = FUN$$
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. **Equation:**
$$8 \times (100A + 10M + C) = 100F + 10U + N$$
5. **Analyze the multiplication:**
Since $A$, $M$, $C$, $F$, $U$, $N$ are digits 1-9 and distinct, and $8 \times AMC = FUN$, $FUN$ must be a three-digit number.
6. **Consider the last digit $N$:**
The last digit of $FUN$ is $N$, which equals the last digit of $8 \times AMC$.
The last digit of $8 \times AMC$ depends on the last digit of $AMC$, which is $C$.
So:
$$N = (8 \times C) \mod 10$$
7. **Try possible values for $C$ (1 to 9):**
- $C=1 \Rightarrow N=8$
- $C=2 \Rightarrow N=6$
- $C=3 \Rightarrow N=4$
- $C=4 \Rightarrow N=2$
- $C=5 \Rightarrow N=0$ (not allowed, digits are non-zero)
- $C=6 \Rightarrow N=8$
- $C=7 \Rightarrow N=6$
- $C=8 \Rightarrow N=4$
- $C=9 \Rightarrow N=2$
Possible $N$ values are $2,4,6,8$.
8. **Check the carry and digit constraints:**
Since $8 \times AMC$ is a three-digit number $FUN$, $F$ must be 1 or less because $8 \times 999 = 7992$ (4 digits), so $F$ is likely 7 or less.
Try $F=7$ (since $8 \times 8xx$ can be near 7xx):
Try $A=1$ (smallest digit), then $AMC$ is about 100+.
Calculate $8 \times 123 = 984$ (digits 9,8,4) which fits pattern $FUN$.
Check if digits are distinct and non-zero:
$A=1$, $M=2$, $C=3$, $F=9$, $U=8$, $N=4$.
Digits are distinct and non-zero.
Check last digit $N=4$ matches $8 \times C = 8 \times 3 = 24$, last digit 4.
This matches.
9. **Answer:**
The digit $N$ represents is $4$.
**Final answer:** $\boxed{4}$