MathDB
Square of a Two-Digit Number

Source:

June 8, 2009

Problem Statement

If the square of a number of two digits is decreased by the square of the number formed by reversing the digits, then the result is not always divisible by: <spanclass=latexbold>(A)</span> 9<spanclass=latexbold>(B)</span> the product of the digits<spanclass=latexbold>(C)</span> the sum of the digits<spanclass=latexbold>(D)</span> the difference of the digits<spanclass=latexbold>(E)</span> 11 <span class='latex-bold'>(A)</span>\ 9 \qquad <span class='latex-bold'>(B)</span>\ \text{the product of the digits}\qquad <span class='latex-bold'>(C)</span>\ \text{the sum of the digits}\qquad <span class='latex-bold'>(D)</span>\ \text{the difference of the digits}\qquad <span class='latex-bold'>(E)</span>\ 11