2021MAA美国数学竞赛AMC10A 秋（含官方解答）.pdf

Official Solutions F MAA American Mathematics Competitions A 23rd Annual L AMC 10 A L Wednesday, November 10, 2021 This official solutions booklet gives at least one solution for each problem on this year’s competition and shows that all problems can be solved without the use of a calculator. When more than one solution is provided, this is done to illustrate a significant contrast in methods. These solutions are by no means the only ones possible, nor are they necessarily superior to others the reader may devise. Teachers are encouraged to share copies of the problem booklet and official solutions with their students for edu- cational purposes. All problems should be credited to the MAA AMC (for example, “2017 AMC 12 B, Problem #21”). The publication, reproduction, or communication of the competition’s problems or solutions for revenue- generating purposes requires written permission from the Mathematical Association of America (MAA). Questions and comments about this competition should be sent to amcinfo@maa.org or MAA American Mathematics Competitions P.O. Box 471 Annapolis Junction, MD 20701. The problems and solutions for this AMC 10 A were prepared by the MAA AMC 10/12 Editorial Board under the direction of Azar Khosravani and Carl Yerger, co-Editors-in-Chief.