Question:

Two finite sets have $m$ and $n$ elements. The total number of subsets of the first set is $56$ more than the total number of subsets of the second set. The values of $m$ and $n$ are

Updated On: Jul 7, 2022
  • m = 7, n = 6
  • m = 6, n = 3
  • m = 5, n = 1
  • m = 8, n = 7
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The Correct Option is B

Solution and Explanation

Let A and B be such sets, i.e, n (A) = m and n (B) = n So, number of subsets of $A = 2^m$ Number of subsets of $B = 2^n$ According to the question, $2^m - 2^n = 56$ $\Rightarrow \, 2^n (2^{m - n} - 1) = 56 = 2^3.7$ Thus, $n = 3$ and $2^{m - n} - 1 = 7$ $\Rightarrow \, n = 3$ and $m - n = 3 $ Hence, we get n = 3 and m = 6
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Concepts Used:

Operations on Sets

Some important operations on sets include union, intersection, difference, and the complement of a set, a brief explanation of operations on sets is as follows:

1. Union of Sets:

  • The union of sets lists the elements in set A and set B or the elements in both set A and set B.
  • For example, {3,4} ∪ {1, 4} = {1, 3, 4}
  • It is denoted as “A U B”

2. Intersection of Sets:

  • Intersection of sets lists the common elements in set A and B.
  • For example, {3,4} ∪ {1, 4} = {4}
  • It is denoted as “A ∩ B”

3.Set Difference:

  • Set difference is the list of elements in set A which is not present in set B
  • For example, {3,4} - {1, 4} = {3}
  • It is denoted as “A - B”

4.Set Complement:

  • The set complement is the list of all elements present in the Universal set except the elements present in set A
  • It is denoted as “U-A”