MathDB
Factorial sums

Source: AMC 10 2006B, Problem 11

February 17, 2006
factorialAMC

Problem Statement

What is the tens digit in the sum 7! \plus{} 8! \plus{} 9! \plus{} \cdots \plus{} 2006!? <spanclass=latexbold>(A)</span>1<spanclass=latexbold>(B)</span>3<spanclass=latexbold>(C)</span>4<spanclass=latexbold>(D)</span>6<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> 4 \qquad <span class='latex-bold'>(D) </span> 6 \qquad <span class='latex-bold'>(E) </span> 9