MathDB
1998 Gauss (7) #25

Source:

February 26, 2017
Gauss

Problem Statement

Two natural numbers, pp and qq, do not end in zero. The product of any pair, p and q, is a power of 10 (that is, 10,100,1000,1000010, 100, 1000, 10 000 , ...). If p>qp >q, the last digit of pqp – q cannot be
<spanclass=latexbold>(A)</span> 1<spanclass=latexbold>(B)</span> 3<spanclass=latexbold>(C)</span> 5<spanclass=latexbold>(D)</span> 7<spanclass=latexbold>(E)</span> 9<span class='latex-bold'>(A)</span>\ 1 \qquad <span class='latex-bold'>(B)</span>\ 3 \qquad <span class='latex-bold'>(C)</span>\ 5 \qquad <span class='latex-bold'>(D)</span>\ 7 \qquad <span class='latex-bold'>(E)</span>\ 9