Competition problem — Combinatorics

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Combinatorics Difficulty 2.0 Junior Find the answer

If $M \subseteq \{1, 2, 3\}$ , and $2 \notin M$ , then the number of all sets $M$ that satisfy the condition is

Pick one

Solution

Given that $M \subseteq \{1, 2, 3\}$ , and $2 \notin M$ , we can easily find that the sets $M$ satisfying the conditions are $\{2\}$ , $\{1, 2\}$ , $\{2, 3\}$ , $\{1, 2, 3\}$ , totaling 4 sets. Thus, we can obtain the answer.

The correct answer is $\boxed{\text{B: 4}}$ .

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Source: NuminaMath-1.5, licensed Apache-2.0. Statement and solution reproduced as published; topic and difficulty added by this site.