Question

If A and B are two sets such that A ⊂ B then, what is A ∪ B?

Answer 1

Let us consider A ⊂ B 

Set A = {1, 2, 3} and 

Set B = {1, 2, 3, 4, 5} 

Now A ∪ B = {1, 2, 3} ∪ {1, 2, 3, 4, 5} 

= {1, 2, 3, 4, 5} = B 

∴ A ∪ B = B