# 1980 AHSME Problems/Problem 15

## Problem

A store prices an item in dollars and cents so that when 4% sales tax is added, no rounding is necessary because the result is exactly $n$ dollars where $n$ is a positive integer. The smallest value of $n$ is $\text{(A)} \ 1 \qquad \text{(B)} \ 13 \qquad \text{(C)} \ 25 \qquad \text{(D)} \ 26 \qquad \text{(E)} \ 100$

## Solution

Say that the price of the item in cents is $x$ (so $x$ is a positive integer as well). The sales tax would then be $\frac{x}{25}$, so $n=\frac{1}{100}\left( x+\frac{x}{25}\right)=\frac{26x}{2500}=\frac{13x}{1250}$.

Since $x$ is positive integer, the smallest possible integer value for $n=\frac{13x}{1250}$ occurs when $x=1250$, which gives us the answer $\fbox{\text{(B)13}}$.

## See also

 1980 AHSME (Problems • Answer Key • Resources) Preceded byProblem 14 Followed byProblem 16 1 • 2 • 3 • 4 • 5 • 6 • 7 • 8 • 9 • 10 • 11 • 12 • 13 • 14 • 15 • 16 • 17 • 18 • 19 • 20 • 21 • 22 • 23 • 24 • 25 • 26 • 27 • 28 • 29 • 30 All AHSME Problems and Solutions

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