Final Cover - For Printing

In the above two sets, as no element is common and hence the sets A and B are non-

overlapping sets.

To enable the child to understand the concept, provide two different sets of objects,

say, pen, pencil, eraser in one hand and stylus, scale, abacus on the other hand. Now

ask the child to explore the objects in his hands and the child will be able to realize

that among the two sets there exists no common object, and hence the two sets are

non- overlapping sets.

25. Set difference
    If A and B are any two sets, then the set of all elements of A which are not in B is
    called the difference set which is denoted as A-B. Note that A-B and B-A are not
    equal.

Eg. : If A = {1, 2, 3}

B = {3, 4, 5}

Then A - B = {1, 2}

Also, B – A = {4, 5}

The idea may be explained to the child orally supported by relevant text material in
Braille. If the child is still not clear with the idea, the methodology followed in
teaching the concepts of union and intersection of sets, with the same objects may
be followed.

26. Symmetric difference
    The symmetric difference of two sets A and B is the union of their difference sets
    (A-B) and (B-A), denoted as the set (A-B)^ ∪ (B-A). The symmetric difference of two
    sets A and B is denoted as AΔB and is read as A delta B.

i.e., AΔB = (A-B) ∪^ (B-A)