If AB, then A∩B = AB.
Always
Sometimes
Never
Which one?

Question

If AB, then A∩B = AB.
Always
Sometimes
Never 
Which one?

parthkohli · Answer

Incomplete!

parthkohli · Answer

If AB what?

anonymous · Answer

its supposed to bb A sidways u and B

swissgirl · Answer

$A \cap B=A \subseteq B$

parthkohli · Answer

Oh,$$\rm A\subset B$$A is a subset of B.

anonymous · Answer

@swissgirl yup thats how it looks how u type that?

zarkon · Answer

if $A\subset B$ then $A\cap B$=A

swissgirl · Answer

\ (A\cap B=A \subseteq B\ )
If you remove the spaces btwn \ and ( then It will appear

parthkohli · Answer

An example:

Let's define A as {1,2,3} and B as {1,2,3,4,5......}.

Then, $\rm A\cap B = \{1,2,3\} = A$

swissgirl · Answer

$A \cap B$ means the intersection of  A and B
Meaning the elements that both A and B have
Lets draw a diagram
|dw:1349451197948:dw|
The shaded region is the intersection of A and B

parthkohli · Answer

You could say that a new set $\rm A \cap B$ consists of the common elements in $\rm A$ and $\rm B$.

swissgirl · Answer

If $A \subseteq B$, then A∩B = $A \subseteq B$. 
Always 
Sometimes 
Never 
Which one?
Is this the question?

swissgirl · Answer

So $A \subseteq B$
Means that everything in A is everything in B
Meaning A is contained in B
|dw:1349451437835:dw|

swissgirl · Answer

Now we can see that the intersection of A and B is A
|dw:1349451524372:dw|
The whole circle A is the intersection of A and B $ A \cap B $