If A = {1, 2, 3, 4, 5}, how many subsets contain 1 and 2 and exclude 5?
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Answer and explanation
Correct answer: 4
The elements 1 and 2 are required, while 5 is forbidden. Therefore the only elements whose membership is undecided are 3 and 4. Each of these two elements can independently be included or excluded, producing 2² = 4 possible subsets: {1,2}, {1,2,3}, {1,2,4}, and {1,2,3,4}. Hence option B is correct.
Frequently asked questions
What is the correct answer to this question?
4
Why is this the correct answer?
The elements 1 and 2 are required, while 5 is forbidden. Therefore the only elements whose membership is undecided are 3 and 4. Each of these two elements can independently be included or excluded, producing 2² = 4 possible subsets: {1,2}, {1,2,3}, {1,2,4}, and {1,2,3,4}. Hence option B is correct.
Which subject and chapter does this question cover?
This is a Class 10 Mathematics question. Chapter: Sets. Topic: Equal sets and Subsets.
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