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AMC 12 2022a Problem 19

  • Paper

Suppose that 1313 cards numbered 1,2,3,…,131, 2, 3, \ldots, 13 are arranged in a row. The task is to pick them up in numerically increasing order, working repeatedly from left to right. In the example below, cards 1,2,31, 2, 3 are picked up on the first pass, 44 and 55 on the second pass, 66 on the third pass, 7,8,9,107, 8, 9, 10 on the fourth pass, and 11,12,1311, 12, 13 on the fifth pass. For how many of the 13!13! possible orderings of the cards will the 1313 cards be picked up in exactly two passes?

size(11cm);
draw((0,0)--(2,0)--(2,3)--(0,3)--cycle);
label("7", (1,1.5));
draw((3,0)--(5,0)--(5,3)--(3,3)--cycle);
label("11", (4,1.5));
draw((6,0)--(8,0)--(8,3)--(6,3)--cycle);
label("8", (7,1.5));
draw((9,0)--(11,0)--(11,3)--(9,3)--cycle);
label("6", (10,1.5));
draw((12,0)--(14,0)--(14,3)--(12,3)--cycle);
label("4", (13,1.5));
draw((15,0)--(17,0)--(17,3)--(15,3)--cycle);
label("5", (16,1.5));
draw((18,0)--(20,0)--(20,3)--(18,3)--cycle);
label("9", (19,1.5));
draw((21,0)--(23,0)--(23,3)--(21,3)--cycle);
label("12", (22,1.5));
draw((24,0)--(26,0)--(26,3)--(24,3)--cycle);
label("1", (25,1.5));
draw((27,0)--(29,0)--(29,3)--(27,3)--cycle);
label("13", (28,1.5));
draw((30,0)--(32,0)--(32,3)--(30,3)--cycle);
label("10", (31,1.5));
draw((33,0)--(35,0)--(35,3)--(33,3)--cycle);
label("2", (34,1.5));
draw((36,0)--(38,0)--(38,3)--(36,3)--cycle);
label("3", (37,1.5));

(A) 4082(B) 4095(C) 4096(D) 8178(E) 8191\textbf{(A) } 4082 \textbf{(B) } 4095 \textbf{(C) } 4096 \textbf{(D) } 8178 \textbf{(E) } 8191

Dataset text AMC 12 2000 to 2025. Quoted with source.

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D

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