If A = {a, b, c, d, e}, how many subsets of A contain at least 4 elements?
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Answer and explanation
Correct answer: 6
At least 4 elements means that the subset may contain exactly 4 elements or exactly 5 elements. The number of four-element subsets is C(5,4) = 5, because one element is omitted. The only five-element subset is A itself, counted by C(5,5) = 1. Hence the total is 5 + 1 = 6, so option B is correct.
Frequently asked questions
What is the correct answer to this question?
6
Why is this the correct answer?
At least 4 elements means that the subset may contain exactly 4 elements or exactly 5 elements. The number of four-element subsets is C(5,4) = 5, because one element is omitted. The only five-element subset is A itself, counted by C(5,5) = 1. Hence the total is 5 + 1 = 6, so option B is correct.
Which subject and chapter does this question cover?
This is a Class 10 Mathematics question. Chapter: Sets. Topic: Power Set and Subsets.
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