Olympiad Maths Prep

Track / Stage 4 / 36 of 340 #296 of 2000

Problem 296

AMC 12 late, AIME early
Combinatorics Difficulty 4.6 Find the answer

1. Given the universal set I={1,2,3,4,5},ABI=\{1,2,3,4,5\}, A \cap B ={2},AˉB={1,4}=\{2\}, \bar{A} \cap B=\{1,4\}. Then Bˉ\bar{B} equals: ( ).
(A) {3}\{3\}
(B) {5}\{5\}
(C) {1,2,4}\{1,2,4\}
(D) {3,5}\{3,5\}

This one wants a proof. Work it on paper, read the official solution, then mark yourself honestly — the ladder only means something if the record is true.

Official solution

1. D

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