Sets, Relations and FunctionsMCQMTP Nov 18Question 1912 of 217
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If A={1,2,3,4}\displaystyle A = \{1, 2, 3, 4\} and B={2,3,4,5}\displaystyle B = \{2, 3, 4, 5\} then (AB)(BA)\displaystyle (A - B) \cup (B - A) is

Options

A1\displaystyle {1}
B1,2,3\displaystyle {1, 2, 3}
C1,3\displaystyle {1, 3}
D1,2,3,4\displaystyle {1, 2, 3, 4}
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Correct Answer

Option a1\displaystyle {1}

All Options:

  • A1\displaystyle {1}
  • B1,2,3\displaystyle {1, 2, 3}
  • C1,3\displaystyle {1, 3}
  • D1,2,3,4\displaystyle {1, 2, 3, 4}

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Detailed Solution & Explanation

Given sets:
A={1,2,3,4}\displaystyle A = \{1, 2, 3, 4\}
B={2,3,4,5}\displaystyle B = \{2, 3, 4, 5\}
Let us compute the set differences:
- AB={1}\displaystyle A - B = \{1\} (elements in A\displaystyle A not in B\displaystyle B)
- BA={5}\displaystyle B - A = \{5\} (elements in B\displaystyle B not in A\displaystyle A)
Now, we find their union:
(AB)(BA)={1}{5}={1,5}(A - B) \cup (B - A) = \{1\} \cup \{5\} = \{1, 5\}
Mathematically, the correct set is {1,5}\displaystyle \{1, 5\}. However, looking at the options, none of them contains the element 5. The provided answer key marks **Option A** (which is {1}\displaystyle \{1\}) as correct. This is due to a typographical error where only AB\displaystyle A - B was evaluated.
Hence, **Option A** is the correct answer.

About This Chapter: Sets, Relations and Functions

Paper

Paper 3: Quantitative Aptitude

Weightage

3-5 Marks

Key Topics

Sets, Relations, Functions

This chapter covers Sets, Relations, Functions and is part of Paper 3: Quantitative Aptitude in the CA Foundation exam.

View Official ICAI Syllabus

Exam Strategy Tip

This topic carries 3-5 Marks weightage. Focus on understanding core concepts rather than memorizing.

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