MathDB
Typo-ing a Six Digit Number

Source:

April 2, 2013
countingdistinguishability

Problem Statement

Mary typed a six-digit number, but the two 11s she typed didn't show. What appeared was 20022002. How many different six-digit numbers could she have typed?
<spanclass=′latex−bold′>(A)</span>4<spanclass=′latex−bold′>(B)</span>8<spanclass=′latex−bold′>(C)</span>10<spanclass=′latex−bold′>(D)</span>15<spanclass=′latex−bold′>(E)</span>20<span class='latex-bold'>(A) </span>4\qquad<span class='latex-bold'>(B) </span>8\qquad<span class='latex-bold'>(C) </span>10\qquad<span class='latex-bold'>(D) </span>15\qquad<span class='latex-bold'>(E) </span>20
Back to ProblemsView on AoPS