1984 AIME Problems/Problem 2

Problem

The integer $n$ is the smallest positive multiple of $15$ such that every digit of $n$ is either $8$ or $0$ . Compute $\frac{n}{15}$ .

Solution

Any multiple of 15 is a multiple of 5 and a multiple of 3.

Any multiple of 5 ends in 0 or 5; since $n$ only contains the digits 0 and 8, the units digit of $n$ must be 0.

The sum of the digits of any multiple of 3 must be divisible by 3. If $n$ has $a$ digits equal to 8, the sum of the digits of $n$ is $. For this number to be divisible by 3,$ a $must be divisible by 3. We also know that$ a>0 $since$ n $is positive. Thus$ n$must have at least three copies of the digit 8.

The smallest number which meets these two requirements is 8880. Thus the answer is$ (Error compiling LaTeX. Unknown error_msg)\frac{8880}{15} = \boxed{592}$.

1984 AIME (Problems • Answer Key • Resources)
Preceded by Problem 1	Followed by Problem 3
1 • 2 • 3 • 4 • 5 • 6 • 7 • 8 • 9 • 10 • 11 • 12 • 13 • 14 • 15
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1984 AIME Problems/Problem 2

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