UPSC NDA Math Model Paper 3

We know the use and importance of Venn diagram, let’s check which relationships are correct.
1. (A - B) ∪ B = A
Here if we take union of (A – B) and B we will get union of A and B It means, this statement is incorrect.
2. (A - B) ∪ A = A
From the above Venn diagram, we can easily say that this statement is correct.
3. (A - B) ∩ B = ϕ
There is no common region between (A – B) and B so the result will be null (ϕ)
This statement is correct.
4. A ⊆ B ⇒ A ∪ B = B
Here A is subset of B that means set A is contained inside set B,
If we take union of both A and B, the obvious result will be B
This statement is also correct.
From above analysis we can say statement (2), (3), and (4) are correct.
Hence option 2 is correct.