If A is a non-empty set such that the power set of A is P(A) = {ϕ, {1}, {2}, {3}, {1, 2}, {2, 3}, {1, 3}, {1, 2, 3}} then find the set A ?

  1. {1}
  2. {1, 2}
  3. {1, 2, 3}
  4. None of these

Answer (Detailed Solution Below)

Option 3 : {1, 2, 3}
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Detailed Solution

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CONCEPT:

Power Set:

Let A be set, then the set of all the possible subsets of A is called the power set of A and is denoted by P(A).

Note: If A is a finite set with m elements. Then the number of elements (cardinality) of the power set of A is given by: n (P(A)) = 2m.

CALCULATION:

Given: A is a non-empty set such that the power set of A is P(A) = {ϕ, {1}, {2}, {3}, {1, 2}, {2, 3}, {1, 3}, {1, 2, 3}}

Here, we have to find the set A

As we know that, if A is a set then the power set of A is given by P(A) = {X : X ⊆ A}

So, we can clearly see from the definition of the power set of A that A = {1, 2, 3}

Hence, the correct option is 3.

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